hemlock (n.) Look up hemlock at Dictionary.com
a poisonous plant, Old English (Kentish) hemlic, earlier hymlice, hymblice; of unknown origin. Liberman suggests from root hem- "poison," perhaps with the plant name suffix -ling or -ig. As the name of the poison derived from the plant, c.1600. The North American tree so called from 1776, from resemblance of its leaves to those of the plant.