'little-used' is a modern English compound formed from 'little' + the past participle 'used' (from the verb 'use'). 'Little' originates from Old English 'lytel' meaning 'small' or 'not much', and 'use' ultimately comes from Latin via Old French (Latin 'uti' → Old French 'user').

The element 'used' is the past participle of 'use', which entered English via Old French 'user' (from Latin 'uti') in the Middle English period. The compounding pattern (adjective formed from 'little' + past participle) became productive in modern English, producing forms like 'little-used' by the 18th–19th centuries.

Originally a literal combination meaning 'used little' (i.e., having little use), it has been established as an adjectival phrase meaning 'seldom used' with essentially the same basic sense.