pēnĭcŭlus (noun M) : dim.penis, lit., a little tail; hence
* A brush for removing dust (for which ox-tails and horse-tails were used): (a pene) peniculi, quis calciamenta tergentur, quod e codis extremis faciebant antiqui, etc.,Fest. p. 230 Müll.: juventus nomen fecit Peniculo mihi, ideo quia mensam, quando edo, detergeo,Plaut. Men. 1, 1, 1; cf.: Quis iste'st Peniculus? Qui extergentur baxeae?id. ib. 2, 3, 40.
* A sponge: ut peniculus novos exurgeri solet,Plaut. Rud. 4, 3, 69; Ter. Eun. 4, 7, 7; Amm. 15, 5, 4; cf.: peniculi spongiae longae propter similitudinem caudarum appellatae, Paul. ex Fest. p. 208 Müll.
* A painter's brush or pencil, Dig. 33, 7, 17.
* Perh., in an ambiguous sense, = membrum virile, Plaut. Men. 2, 2, 12.

s. TLL