the compound adjective 'warmed-over' is a relatively modern american english formation from the late 19th century, originally describing food that had been cooked, allowed to cool, and then reheated. it is built transparently from the past participle 'warmed' and the adverb 'over', with 'over' here implying a process applied again or anew. by the mid-20th century, its meaning was extended metaphorically to describe ideas, stories, or arguments that are stale, unoriginal, and presented as if they were new, drawing a direct analogy to the diminished appeal of reheated food.

Structure: warmed + over warmed (past participle of the verb 'warm', from old english 'werman'/'wearmian', meaning to make or become warm); over (adverb/preposition, from old english 'ofer', meaning above or across)