c. 1300, "fact or condition of thriving," also "prosperity, savings," from Middle English thriven "to thrive" (see thrive), influenced by (or from) Old Norse þrift, variant of þrif "prosperity," from þrifask "to thrive." Sense of "habit of saving, economy" first recorded 1550s (thrifty in this sense is recorded from 1520s; also see spendthrift). Thrift shop attested by 1919.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).