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.
popular name of a common type of forest tree of Eurasia, North America, and North Africa, Middle English asshe, from Old English æsc "ash tree," from Proto-Germanic *askaz, *askiz (source also of Old Norse askr, Old Saxon ask, Middle Dutch esce, German Esche), from PIE root *os- "ash tree" (source also of Armenian haci "ash tree," Albanian ah "beech," Greek oxya "beech," Latin ornus "wild mountain ash," Russian jasen, Lithuanian uosis "ash").
The close-grained wood of the ash is tough and elastic, and it was the preferred wood for spear-shafts, so Old English æsc sometimes meant "spear," especially in poetry, as in æsc-here "company armed with spears," æsc-plega "war," literally "spear-play." Æsc also was the name of the Old English runic letter that begins the word.
"powdery remains of fire," Middle English asshe, from Old English æsce "ash," from Proto-Germanic *askon (source also of Old Norse and Swedish aska, Old High German asca, German asche, Middle Dutch asche, Gothic azgo "ashes"), from PIE root *as- "to burn, glow." Spanish and Portuguese ascua "red-hot coal" are Germanic loan-words.
An ancient symbol of grief or repentance; hence Ash Wednesday (c. 1300), from the custom introduced by Pope Gregory the Great of sprinkling ashes on the heads of penitents on the first day of Lent. Ashes meaning "mortal remains of a person" is attested from late 13c., in reference to the ancient custom of cremation. The meaning "finely pulverized lava thrown from a volcano" is from 1660s.