refuse: [14] Refuse comes via Old French refuser from an unrecorded Vulgar Latin *refūsāre. It is not altogether clear where this came from, for it has no direct Latin antecedent. One theory is that it represents a blend of Latin recūsāre ‘refuse’ (source of English recusant [16]), a compound verb based on causa ‘cause’, and refūtāre ‘rebut’ (source of English refute [16]), a compound verb based on the element *fūt-, found also in English confute [16].
But another long-established school of thought derives it from refūsus, the past participle of Latin refundere ‘pour back’ (source of English refund [14]) – the underlying notion being of something ‘poured back’ or ‘rejected’. The noun refuse ‘rubbish’ [15] probably comes from Old French refus ‘refusal’, a derivative of refuser ‘refuse’. [refuse etymology, refuse origin, 英语词源]