Grunt
Old English grunnettan, of Germanic origin and related to German grunzen ; probably originally imitative.
wiktionary
From Middle English grunten, from Old English grunnettan(“to grunt”), from Proto-Germanic *grunnatjaną(“to grunt”), frequentative of Proto-Germanic *grunnōną(“to grunt”), from Proto-Indo-European *gʰrun-(“to shout”).
Cognate with German grunzen(“to grunt”), Danish grynte(“to grunt”). The noun senses are all instances of zero derivation from the verb. [1]
etymonline
grunt (v.)
Old English grunnettan "to grunt," frequentative of grunian "to grunt," probably imitative (compare Danish grynte, Old High German grunnizon, German grunzen "to grunt," French grogner, Latin grunnire "to grunt"). Related: Grunted; grunting. Grunter "a pig" is from 1640s.
grunt (n.)
1550s, from grunt (v.); as a type of fish, from 1713, so called from the noise they make when hauled from the water; 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.
