Lewis & Short

pēnis, is, m. (abl. peni, Naev. ap. Fest. p. 230 Müll.) [τὸ πέος], a tail.

  1. I. In gen. (ante-class.): caudam antiqui penem vocabant, Cic. Fam. 9, 22, 2: … lares ludentes peni pinxit bubulo, Naev. ap. Fest. p. 230 Müll.
  2. II. In partic., = membrum virile, the penis; also, by meton., for lust (class.): hodie penis est in obscenis, Cic. Fam. 9, 22, 2: ganeo, manu, ventre, pene bona patria laceraverat, Sall. C. 14, 2; Hor. Epod. 12, 8; Juv. 9, 43; Arn. 5, 18.
    In a paron. with paene, Plaut. Truc. 2, 6, 37.