The alliteration is delightful, and its meaning is lucid, ascertainabled from each of its component parts: pusillus (very small) animous (spirit). To my mind, pusillus could be further deconstructed. Many Latin _pu_ words pertain to power, and the stem _il_ is dimunitive, thereby rendering the meaning of pussilus something along the lines of "little power," which may also explain why the Latin term pussilus referred to a young boy.