In Virgil Georgics III is this text, in a description (which makes me think of Ice Road Truckers) of a winter in the steppes back of the Sea of Azov :-
Interea toto non setius aere ninguit:
intereunt pecudes, stant circumfusa pruinis
corpora magna boum, confertoque agmine cervi
torpent mole nova et summis vix cornibus extant.
What does "setius" mean exactly? I cannot find it in my good big voluminous Latin to English dictionary. Google ...