early 15c., "dissolved, of loose structure," also "morally lax," from Latin resolutus, past participle of resolvere "untie, unfasten, loose, loosen" (see resolution). Meaning "determined, decided, absolute, final" is from c.1500, especially in resolute answer, a phrase "common in 16th c." [OED]. From 1530s of persons. The notion is of "breaking (something) into parts" as the way to arrive at the truth of it and thus make the final determination (cf. resolution). Related: Resolutely; resoluteness.