fătŭĭtas, ātis, f. [1. fatuus],
foolishness , folly , silliness , fatuity (very rare), Cic. Inv. 2, 32, 99; id. Att. 11, 25, 2; Firm. Math. 8, 19; Vulg. Prov. 16, 22; August. Ep. 65.
fatuitās ātis, f fatuus, folly, fatuity . ...
An Elementary Latin Dictionary