grunt (v.) Look up grunt at Dictionary.com
Old English grunnettan "to grunt," frequentative of grunian "to grunt," probably imitative (compare Danish grynte, Old High German grunnizon, German grunzen "to grunt," Latin grunnire "to grunt"). Related: Grunted; grunting.
grunt (n.) Look up grunt at Dictionary.com
1550s, from grunt (v.); as a type of fish, from 1713; meaning "infantry soldier" emerged in U.S. military slang during Vietnam War (first recorded in print 1969); used since 1900 of various low-level workers. Grunt work first recorded 1977.