Origin and history of tedium

"tediousness, weariness," 1660s, from Latin taedium "weariness, irksomeness, disgust" (mostly post-classical), which is related to taedet "it is wearisome, it excites loathing" (in Late Latin "be disgusted with, be weary of") and to taedere "to weary," but the whole group is of uncertain etymology. Possible cognates that have been suggested are Old Church Slavonic težo, Lithuanian tingiu, tingėti "to be dull, be listless."

Caxton (late 15c.) has tedeation "act of wearying, condition of being wearied." A verb tedify "to bore, affect with tedium" is attested by 1610s (hence tedification), as is the noun tediosity.