Lewis & Short

ūlīgo, ĭnis, f. [contr. from uviligo, from uveo, uvens, uvesco, uvidus, etc.], moisture, marshy quality of the earth (syn. umor), Varr. R. R. 2, 2, 7; Col. 1, 6, 16; 2, 9, 9; Verg. G. 2, 184; cf. Serv. ad loc.; Sil. 8, 381; Tac. A. 1, 64.