cūlus, i, m. [perh. kindr. with κοῖλος, of a curving form; cf. 1. anus],
the posteriors, fundament , Cat. 23, 19; 33, 4; 97, 2; Mart. 3, 98, 1.
cūlus ī, m the fundament, Ct. ...
An Elementary Latin Dictionary