Fuck is the perfect adjective, adverb, verb, noun.
As to the origin - ?? Does it even matter?
It is a reliable emphatic expression for joy, grief, love, disgust, hate -disappointment,personality. It is at once a superior noun, verb, adverb, adjective - every glorious part of speech. It's fucking perfect!
1. It is unpleasant sounding - uncouth,unmannerly, impolite, potty-mouth language - I can't say it and can barely type it.
2. Fart (not found in the dictionary) - as above. Both are unnecessary. "Pee" is acceptable - if reference is required. Piss is a synonym for "take a leak" an equally disgusting verbal description of the same bodily function. YYuck.