late 14c., "a breaking into parts," from Old French resolution (14c.) or directly from Latin resolutionem (nominative resolutio) "process of reducing things into simpler forms," from past participle stem of resolvere "loosen" (see resolve). Sense of "a solving" (as of mathematical problems) first recorded 1540s, as is that of "power of holding firmly" (cf. resolute). Sense of "decision or expression of a meeting" is from c.1600. Meaning "effect of an optical instrument" is from 1860.