- late 14c., originally as an adverb, "moreover, in addition," from Latin item (adv.) "likewise, just so, moreover," used to introduce a new fact or statement. This is probably from ita "thus," id "it" (see id) + adverbial ending -tem (compare idem "the same").
The adverb, in the sense "moreover, in addition," was used in English before every article in a list (such as an inventory or bill). From this comes the noun sense "a statement or maxim" (of the kind formerly introduced by the word item), first recorded 1560s, and eventually "an article of any kind" (1570s). Meaning "detail of information" (especially in a newspaper) is from 1819; item "sexually linked unmarried couple" is 1970, probably from notion of being an item in the gossip columns.