mid-15c., "implying comparison," from Old French comparatif, from Latin comparativus "pertaining to comparison," from comparat-, past participle stem of comparare "make equal with, liken, bring together for a contest," from com "with, together" (see com-) + par "equal" (see par (n.)).
Originally grammatical and applied to derived adjectives such as greater, stronger, softer. General sense of "estimated by comparison, relative" is from 1590s. Meaning "involving the parallel pursuit of different branches of a subject" is from 1670s. Old English used wiðmetendlic as a loan-translation of Latin comparativus. Related: Comparatively.