'non-fused' is built from the prefix 'non-' (from Latin 'non', meaning 'not') combined with 'fused' (from Latin 'fundere'/'fusus', via Old French/Medieval Latin), where 'non-' meant 'not' and the root behind 'fuse' concerned 'pouring' or 'melting'.

'fuse' developed from Latin 'fundere' (to pour) with past participle 'fusus'; it passed into Old French (e.g. 'fuser') and Middle English (e.g. 'fusen') before becoming modern English 'fuse'. The negative prefix 'non-' entered English usage from Latin/Old French as a productive negator attached to adjectives and participles, producing compounds like 'non-fused'.

Originally the Latin root ('fundere') meant 'to pour'; over time the sense shifted to 'melt, join by melting, or cause to combine', so 'fused' came to mean 'joined' and 'non-fused' to mean 'not joined'.