Etymology tree Proto-Indo-European *pes- Proto-Indo-European *pes-ni-s Proto-Italic *peznis Latin pēnislbor. English penis Learned borrowing from Latin pēnis, from Proto-Italic *peznis, from Proto-Indo-European *pes-ni-s, from *pes- (“penis”). First attested in the late 17th century. Displaced native English pintle, tarse, pillicock.