Meaning

noun a distinct part that can be specified separately in a group of things that could be enumerated on a list

noun a small part that can be considered separately from the whole

noun a whole individual unit; especially when included in a list or collection

originFrom Middle English item, from Latin item (“also; in the same manner”). The present English meaning derives from a usage in lists, where the first entry would begin in primis (“firstly”) or imprimis, and the other entries with item (“also, moreover”). Later, the members of lists were referred to as "items".

Etymology from Wiktionary, CC BY-SA 3.0