mid-15c., of wine, "muddy, not clear," from Old French impur (13c.), from Latin impurus "not pure, unclean, filthy, foul," from assimilated form of in- "not, opposite of" (see in- (1)) + purus "pure" (see pure).
In English, the subsequent order of sense appearance seems to be "earthly, mundane, not spiritual" (c. 1500); "obscene, lewd, unchaste, immoral" (1530s); "mixed with offensive matter, tainted" (1590s); "mixed or combined with other things" (without reference to foulness), 1620s. As a noun from 1784. Related: Impurely.
pure form of gelatin, 1848, from Greek kolla "glue," which is of uncertain origin, + chemical suffix -in (2).
c. 1200, purite, "freedom from moral contamination, sinlessness, innocence; righteousness; chastity," from Old French purete "simple truth," earlier purte (12c., Modern French pureté), from Late Latin puritatem (nominative puritas) "cleanness, pureness," from Latin purus "clean, pure, unmixed; chaste, undefiled" (see pure (adj.)). From mid-15c. as "freedom from admixture or adulteration."