'merger-resistant' originates as a compound of 'merger' and 'resistant'. 'Merger' comes from the verb 'merge', which ultimately traces to Latin 'mergere' meaning 'to plunge, immerse', entering English via Old French (sense shifted toward 'combine'); 'resistant' comes from Latin 'resistere' ('re-' + 'sistere') meaning 'to stand back or oppose', via Old French and later English formation.

'merger' changed from Latin 'mergere' → Old French 'merger' → Middle English 'merge/mergen' and eventually became modern English 'merge' and the noun 'merger'; 'resistant' developed from Latin 'resistere' → Old French 'resister' → English 'resist' and then the adjective 'resistant'. The modern compound 'merger-resistant' formed by combining these elements in recent business English.

Initially, 'mergere' meant 'to plunge/sink' and 'resistere' meant 'to stand back/oppose'; over time 'merge' acquired the sense 'to combine' and 'resistant' the sense 'opposed to', so the compound now means 'opposed to or difficult to combine via merger' (i.e., 'resistant to mergers').