Do you find 21st-century life shallow, superficial, obsessed with surfaces? Take another look: In fact, ours is an era of extraordinary depth — linguistically speaking, anyway. Deep is everywhere in science, culture, and technology, with new deep compounds and constructions being added to the lexicon every year, from deepfake and deep web to Deep Medicine (a book title) and Deep-Speare (a Shakespeare emulator). As the 2011 song by Adele put it, we're rolling in the deep.

Deep has deep roots. In Old English, where it was usually spelled deop, it served as noun (shorthand for "the ocean") and adjective ("having considerable extension downward" and also "profound" or "mysterious"). By the early 13th century, people could be called deep if they had sagacious, "penetrating" minds. In the late 14th century, deep took on additional figurative meanings: low-pitched in tone ("a deep voice") or intense ("deep red"). Deep water has been a metaphor for "danger" since Old English, but it took the democratization of swimming pools in the 1920s to make going off the deep end — giving way to anger — a popular colloquialism. And although "six feet deep" and "six fathoms deep" have long meant "where someone is buried" on land and sea, respectively, "to give (something) the deep six" — to reject, abandon, or jettison it — didn't emerge until about 1921; the verb to deep six caught on about three decades later.

The English hard-rock band Deep Purple, which formed in 1968, took its name from the 1933 song "Deep Purple," a favorite of guitarist Ritchie Blackmore's grandmother. In the lyric, "deep purple" is a chromatic metaphor for "twilight."

Deep has attached itself to many other nouns and modifiers over the centuries. Deep sleep has been documented since 1547, but it wasn't until 1968 that scientists identified it as a brain function. We have deep mourning (1722), deep seated (1741), deep time (1832, to describe time in the distant past or future), deep-throated (1844), deep breathing (1904, as a form of exercise), deep-fry (1933), deep-dish pie (1934), deep freeze (1941), and deep pockets (1951, "wealth").

The Watergate scandal, during the Nixon presidency, gave us Deep Throat, the nickname of the anonymous government source who provided crucial leads to the Washington Post reporters Bob Woodward and Carl Bernstein. "Woodstein" borrowed the moniker, semi-ironically, from the title of a 1972 pornographic movie, but it also echoed deep-cover, an early-1960s coinage that refers to a spy whose identity is thoroughly protected.

Modern science and technology have given us new extensions of deep. For linguists, one of the most influential inventions was deep structure, coined by Noam Chomsky in the early 1960s to refer to the underlying syntax of a sentence. But the real deep expansion began in 2000, when deep web and deep learning first appeared.

The deep web — sometimes called the "hidden" or "invisible" web — is the part of the World Wide Web not indexed by standard search engines. A 2015 documentary called Deep Web explored this terra incognita: "decentralized, encrypted, dangerous, and beyond the law." Deep learning, a sub-subset of artificial intelligence (AI), works with unstructured and unlabeled data to create everything from color names to games to medicine … or even Shakespearean sonnets. In 2018, a group of researchers trained a neural network on the Bard's vocabulary and rhyme patterns to develop Deep-Speare, which generated four-line poems that “scored high on rhyme and meter" but "overall lacked readability and emotion." "Deep" here refers to the number of layers through which the data is transformed; deep learning architectures include deep neural networks and deep belief systems.

For investors, deep tech refers to companies based on "substantial scientific advances" and "high tech engineering innovation" that are harder for competitors to replicate — unlike "shallow tech" models such as apps and e-commerce websites. According to a Wikipedia entry, deep tech was coined in 2014 by Swati Chaturvedi, founder of the first deep-tech angel-investing platform.

Star Trek: Deep Space Nine aired for seven seasons between 1993 and 1999. The series takes its name from a fictional space station. According to an OED entry, "deep space" — the regions beyond the solar system or Earth's atmosphere — was first used in a 1952 short story, "Prott," by the science-fiction author Margaret St. Clair.

At the intersection of technology, politics, and culture lies deepfake, which has been in the news lately because of doctored videos of U.S. House of Representatives Speaker Nancy Pelosi. The term emerged in late 2017 on the social-media site Reddit, where a user with the handle "deepfakes" used a machine-learning algorithm — that's the deep part — to superimpose the face of Wonder Woman actress Gal Gadot onto the body of a porn actress — the fake part. The technology spread rapidly, and by June 2019 a UCLA professor writing in the very serious Brookings Institution blog warned that "[w]ith the 2020 election campaign heating up, deepfakes are likely to be part of the landscape, spurring discussions regarding their role in elections and what can be done to minimize their impact."

Then there's the ominous-sounding deep state, a term that surfaced early in the Trump presidency to describe a mythical "cabal of unelected leftist officials lodged deep in the government who are conspiring to thwart the administration's policies, discredit its supporters and ultimately even overturn Trump's election," as the linguist Geoff Nunberg put it in a commentary for NPR. The term originated as early as 1900 in authoritarian countries like Turkey, Pakistan, and the Soviet Union, and was pressed into English-language service by the far-right Breitbart News during the 2016 U.S. presidential election. It was appropriated as the tongue-in-cheek title of the Deep State Radio podcast, which launched in 2017 "as an antidote to the lunacy" of conspiracy theories; and it appears in the title of a British TV series about espionage that also debuted in 2017.

From the original podcast, Deep State Radio has branched out into other endeavors, including Deep State Deep Dives ("one-on-ones with Deep State insiders and newsmakers").

On a less-sinister frontier we have deep house, a variant of the style of electronic music known as "house" that originated in early-1980s Chicago. Deep house — mellower and more relaxed, with powerful vocals and a relatively slow beat — first appeared in print in 1988. Your favorite deep house track might be a deep cut, a term used since at least 2008 to describe a song (or "cut") deemed to be less popular than others on an album. Lately deep cut has expanded its meaning to include "any relatively obscure cultural reference" — a minor character in a movie, for example.

It should by now come as no surprise that deep is shows up frequently in brand naming. Although there have long been "Deep" brands — Deep Sea canned salmon goes back to 1895 — the recent spate of trademark applications is unprecedented: I counted more than 250 "Deep" applications filed with the U.S. Patent and Trademark Office in just the last 12 months. Many of them are for computer-related products and companies: Deep Cyber, Deep Human Learning, Deep Identity, Deep Cube, Deep Edge, MicroDeep — even the paradoxical Deep Surface.

One of the most significant "Deep" trademarks was a deep mystery for 35 years. Deep Note was developed as the sonic trademark, or "sound logo," of the audio-visual engineering company THX; it debuted at the May 25, 1983, premiere of Star Wars: Return of the Jedi. Since then, you've probably heard its "distinctive synthesized crescendo," as Wikipedia puts it, before dozens of movies, video games, and live events. But it wasn't until May 25, 2018, that THX revealed Deep Note's deep secret: the sheet music for the spine-chilling sound. For anyone curious about the genesis of a cultural landmark, it was a profound revelation.

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Nancy Friedman is the chief wordworker at verbal-branding consultancy Wordworking, and the author of a fine blog on naming, branding and more called Fritinancy. Nancy has named a venture-capital firm, a laser hair-removal device, a mobile-money service, and many other companies and products. A former journalist, she still writes or ghostwrites articles, speeches, white papers, and books. Click here to read more articles by Nancy Friedman.

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