soluble (adj.)

late 14c., "capable of being dissolved," from Old French soluble "expungable, eradicable" (13c.), from Late Latin solubilis "that may be loosened or dissolved," from stem of Latin solvere "to loosen, dissolve," from PIE *se-lu-, from reflexive pronoun *s(w)e- (see idiom) + root *leu- "to loosen, divide, cut apart." Meaning "capable of being solved" is attested from 1705. Substances are soluble, not solvable; problems can be either.