1530s, "hard-hearted;" 1540s, "hard, impenetrable as flint," from flint + -y (2). Literal sense of "resembling flint" is from 1640s. Related: Flintily; flintiness.
Entries linking to flinty
flint n.
Old English flint "flint; a type of rock noted for hardness and for giving off sparks when struck," from Proto-Germanic *flintaz (source also of Middle Dutch vlint, Old High German flins, Danish flint), from PIE *splind- "to split, cleave," from root *(s)plei- "to splice, split" (source also of Greek plinthos "brick, tile," Old Irish slind "brick"), perhaps a variant of *spel- (1) "to split, break off." Transferred senses (hardness, etc.) were in Old English.
-y 2
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). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.