crisp (adj.)
Old English crisp "curly," from Latin crispus "curled, wrinkled, having curly hair," from PIE root *(s)ker- (3) "to turn, bend" (see ring (n.)). It began to mean "brittle" 1520s, for obscure reasons, perhaps based on what happens to flat things when they are cooked. Figurative sense of "neat, brisk" is from 1814; perhaps a separate word. As a noun, from late 14c. Potato crisps (the British version of U.S. potato chips) is from 1929.
crisp (v.)
late 14c., "to curl," from crisp (adj.). Meaning "to become brittle" is from 1805. Related: Crisped; crisping.