What is the origin of flinty?
Flinty is an obvious combination of the noun flint “a hard stone, a type of silica” and the adjective suffix –y, from Old English –ig, cognate with German –ig, and related to Greek –ikos and Latin –icus. One odd element here is that the derived, metaphorical sense “unyielding, unmerciful, obdurate” appears in the first half of the 16th century, about 75 years before the literal sense “consisting of flint stone” (in Shakespeare’s Henry VI, Part 1). A second oddity is that the noun flint, which comes from Old English flint, has impeccable cognates with other Germanic languages (Middle Dutch vlint, Old High German flins, Danish flint, Swedish flinta), from a Proto-Indo-European root (s)plei– “to split, splice.” But flint may be related to Greek plínthos “brick, air-dried brick, squared building stone,” except that a non-Greek language is the usual source of Greek terms associated with building and architecture and nouns with the suffix –inthos, such as asáminthos “bathtub,” terébinthos “terebinth tree, turpentine tree”—the ultimate source of English turpentine. Flinty entered English in the first half of the 16th century.