prickly (adj.)
1570s, "spiny, armed with prickles" (originally of holly leaves), from prickle (n.) + -y (2). Figurative sense of "irritable" first recorded 1862. Prickly heat is from 1736, so called for the sensation; prickly pear is from 1760 (earlier prickle pear, 1610s). Related: Prickliness.