A / ānus
noun hapax

ānus

gen. āni · gender masculine · decl. 2nd
related to 2. an- = ἀμφί; prim. signif. a rounding, a circular form; hence also 1. anulus; cf. Varr. L. L. 6, 8, p. 76 Müll.
an iron ring for the feet
an iron ring for the feet, Plaut. Men. 1, 1, 9.