prickly (adj.)

1570s, "spiny, full of sharp points, armed with prickles" (originally of holly leaves), from prickle (n.) + -y (2). Figurative sense of "irritable, quick to anger" is recorded by 1862. Prickly heat "inflammatory disorder of the sweat glands" is from 1736, so called for the sensation; prickly pear, of the fruit of a certain cactus, is from 1760 (earlier prickle pear, 1610s). Related: Prickliness.