From Old English truht, in part from Old French truite, from Late Latin tructa, perhaps from Ancient Greek τρώκτης (trōktēs, “nibbler”), from τρώγω (trōgō, “I gnaw”), from Proto-Indo-European *tere- (“to rub, to turn”). The Internet verb sense originated on BBSes of the 1980s, probably from Monty Python's The Fish-Slapping Dance (1972), though that sketch involved a halibut.
Wikipedia trout (plural trout or trouts)
- Any of several species of fish in Salmonidae, closely related to salmon, and distinguished by spawning more than once.
- Many anglers consider trout to be the archetypical quarry.
- 1922, Michael Arlen, chapter 3/19/2, “Piracy”: A Romantic Chronicle of These Days:
- “This morning,” he said, “We will fish, Turner. We will cast for trout so that we may catch grayling.”
- (UK, pejorative) An elderly woman of dubious sensibilities.
- Look, you silly old trout; you can't keep bringing home cats! You can't afford the ones you have!
Derived terms 
trout (third-person singular simple present trouts, present participle trouting, simple past and past participle trouted)
- (Internet chat) To (figuratively) slap someone with a slimy, stinky, wet trout; to admonish jocularly.