Green’s Dictionary of Slang

dog! excl.

(US) a euph. for damn! excl.

1933		J. Conroy Disinherited 158: By doggies, he makes me tard, always chewin’ the rag.
1934		Z.N. Hurston Jonah’s Gourd Vine (1995) 18: Dog damn! Boy you’re almost as big as I am.
1940		W.R. Burnett High Sierra in Four Novels (1984) 368: Dog it! If you ain’t careful you’ll get as scary as your mother.
1947–53		W. Guthrie Seeds of Man (1995) 261: An’ by doggies, turn right smack dab aroun’.
1948		(con. c.1910s) J. Stevens Big Jim Turner 58: Well, by doggy! That’s news to me.
1948		J.M. Cain Moth (1950) 288: I said to myself: Dog it. You never saw Hosey.
1958		V.S. Naipaul Suffrage of Elvira 125: ‘Oh dog, dog,’ she muttered.
1969		E. Leonard Moonshine War 78: [T]he skinny one said, ‘Dog, I like that tan suit that boy’s got on’.
2001		(con. 1990s) in J. Miller One of the Guys 135: ‘Everybody be like, “Dag! ”’Cause my pager is blue. Everybody be like “Dag!” My shoes is blue. My outfit is blue. They be “Dag, dag,, she blued out”’.

In exclamations

dog on it! (also dog on you!)

a mild expletive.

1826		Glasgow Herald 27 Nov. 4/2: Keep to a side [...] for, dog on it, Moosey’ll have a pistol; and [...] would think nae mair o’ shooting yer as dead as a mawkin.
1834		Noctes Ambrosianae in Blackwood’s Mag. xxxvi 132: Dog on’t, you’ll bring bluid.
1858		‘Sweet Betsey from Pike’ in Lingenfelter et al. Songs of the Amer. West (1968) 43: Dog on you! I’m chock full of strong alkali!
1861		Dundee People’s Jrnl 7 Sept. 2/4: ‘Dog on it! there was ane chield [...] set fire to ane o’ my whiskers’.