c. 1400, "scabby, like a crust, hard," from crust (n.) + -y (2). Figurative use, of persons, "short-tempered, surly, peevish" is from 1560s.
Entries linking to crusty
crust n.
early 14c., "hard outer part of bread," from Old French crouste (13c., Modern French croûte) and directly from Latin crusta "rind, crust, shell, bark," from PIE *krus-to- "that which has been hardened," suffixed form of root *kreus- "to begin to freeze, form a crust." From mid-15c. as "any hard, external portion of comparative thinness;" meaning "outer shell of the earth" is from 1550s.
-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.