The word 'tedium' entered English in the mid-17th century, directly from the Latin noun 'taedium', meaning 'weariness, disgust, or boredom'. This Latin term is derived from the verb 'taedēre', 'to weary or disgust'. The core semantic logic is one of a state of being tired or wearied by something, which has been preserved perfectly in its modern English meaning of a wearisome lack of variety or interest. The journey from the Latin verb describing an action to the English noun describing the resulting state illustrates a common pattern of semantic borrowing.

The word is a simplex loanword from Latin. It cannot be meaningfully segmented into productive morphemes in modern English spelling.