Green’s Dictionary of Slang

pooch n.

also poochie
[? Ger. Putzi, a popular name for a lap-dog]

1. a (small) dog; thus pooch-flop n., dog excrement.

[US]B. Fisher A. Mutt in Blackbeard Compilation (1977) 108: I’m beginning to think that pooch is a jinx to me.
[US]N.Y. Times 17 June 18: Our favorite of the many sorry attempts was the sorry pooch, or towser, impersonated by Phil Dwyer, than whom no dog was ever doggier.
[US]Hecht & Bodenheim Cutie 46: All you do is sink your teeth in my shoulder and make noises like a basket full of hungry pooches.
[US]D. Runyon ‘Dream Street Rose’ in Runyon on Broadway (1954) 47: Blondes with Pomeranian pooches, or maybe French poodles.
[US]W.R. Burnett High Sierra in Four Novels (1984) 378: When he saw the little dog in Roy’s car he started [...] ‘Look, Babe. The pooch!’.
[US]W. Guthrie Seeds of Man (1995) 397: I reckon that’s what become of our little poochie, all right.
[US](con. 1950) E. Frankel Band of Brothers 246: We get rid of the pooch, we get you a big dog, a wolfhound, something we can put a muzzle on.
[US]Ragen & Finston World’s Toughest Prison 813: pooch – A dog or pet.
[US]‘Red’ Rudensky Gonif 105: Tick veered toward the curb to miss hitting a stray pooch.
[US]Fantastic Four Annual 46: Ya gave the blasted pooch a case of heartburn!
[Aus]M. Bail Holden’s Performance (1989) 160: I don’t want to see a single pooch in the theatre. Before you know it they’ll lay a turd on the carpets.
[Ire]J. O’Connor Secret World of the Irish Male (1995) 156: She’d better cough up with five hundred smacker pretty pronto or else poochie would be pushing up the daisies.
[US]Source Oct. 116: And the daters try to find a mate for their in-heat pooch.
[UK]Observer 30 Jan. 7: Vet Charles Papapetrou prepares a pooch for acupuncture.
[UK]Guardian 18 Dec. 24/5: Pet Products people have come up with a dog chew advent calendar. Religiously inclined pooches can open a day and get a different object to chew .
[US]J. Hannaham Didn’t Nobody Give a Shit 117: The ladies had brought a dog and a toddler into the shop, and both the pooch and the kid kept losing their minds.

2. (US teen) a Greyhound bus [play on dog, the n.1 ].

[Aus]J. Birmingham Tasmanian Babes Fiasco (1998) 228: I’d caught a Greyhound to the coast. Rode that pooch from Ipswich to deliverance.
Ed Begley ‘Long Trips’ on 🌐 I took Greyhound on a few occasions and since they are nearly always full (unlike Amtrak), I wound up getting around 400 miles per gallon (per passenger) every time I rode the pooch.

3. (N.Z. prison) a drug detection dog.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 143/1: pooch n. the police narcotics detection dog.

In derivatives

poochy (n.)

(US black) a sweetheart.

[US]E. Freeman ‘The Whirling Hub’ in Afro-American (Baltimore, MD) 20 Apr. 15/2: Miss R.P. may be in Canton but she is his poochy.