who came up with the word penis?

Answer 1

it comes from the word "tail", which is strange since the tail is on the other side :-)
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--1676, perhaps from Fr. pénis or directly from L. penis "penis," earlier "tail" (cf. Eng. tail in both senses, the sexual one slang), from PIE *pes-/*pesos- "penis" (cf. Skt. pasas-, Gk. peos, posthe "penis," probably also O.E. fæsl "progeny, offspring," O.N. fösull, Ger. Fasel "young of animals, brood"). The proper plural is penes. The adj. is penial. In psychological writing, penis envy is attested from 1924.