Lewis & Short

sĕvērĭtūdo, ĭnis, f. [1. severus], gravity, austerity, severity (ante- and post-class. for the class. severitas): (frontis) Plaut. Ep. 5, 1, 3 (also cited Non. 173, 10): morum, App. M. 1, p. 113, 41.