Green’s Dictionary of Slang

a euph. for Jesus! and used as such in oaths (cf. jiminy! excl.).

1672		Dryden Assignation II iii: O gemini! is it you, sir?
1681		Otway Soldier’s Fortune II i: Gemini! what would become of me?
1695		Congreve Love for Love II i: O Gemini!
1700		Farquhar Constant Couple IV i: O gemini! my Jubilee pistols!
1707		J. Shirley Triumph of Wit 33: O Gemini! why this is contrary to the received custom.
1722		S. Centlivre Artifice Act IV: O Gemini! What do you do?
1731		C. Coffey Devil to Pay II i: Oh Gemini! who’s this?
1740		Dialogue between a Married Lady and a Maid III: My Mother taking Notice of the Bigness of it. Gemini! said she, what a Monster is this!
1764		Foote Liyr in Works (1799) I 284: O Gemini! I beg a million of pardons.
1775		Sheridan Rivals (1776) II ii: O gemini! and I have been waiting for your worship here on the North.
1780		H. Cowley Belle’s Stratagem IV ii: Oh gemini! beg the petticoat’s pardon.
1794		W. Godwin Caleb Williams (1966) 73: ‘By Gemini,’ said he ‘my heart was in my mouth.’.
1801		‘Peter Pindar’ ‘Orson and Ellen’ Works (1801) V 387: [She] wak’d with dread and fear; And cry’d [...] O gemini! what’s here?
1827		T. Morton A School For Grown Children I i: Gemini! how genteel!
1833		‘Firing Up The Chimney’ in Lummy Chaunter 79: Crikey! gemini!
1843		Satirist & Sporting Chron. (Sydney) 4 Feb. 2/4: It’s devilish odd what’s become of the shop R.C. Cant [...] oh Gemini.
1848		Talfourd & Seymour Sir Rupert, the Fearless I iii: Oh! gemini!
1854		Brookville Jeffersonian (PA) 8 Apr. 1/4: ‘Gee-mi-ny! jest to think of Pete [...] for him to know his old daddy was made a fool of too!’.
1865		Leaves from Diary of Celebrated Burglar 70/2: As we rattled along we turned out the ‘poke,’ and oh! gemini!— one hundred and forty-five pounds in bank of England notes in one end, and three ‘quid’ and some ‘pewter’ in the other.
1876		‘Mark Twain’ Tom Sawyer 20: I wish to gee-miny she’d stick to one or t’other – I can’t keep the run of ’em. [Ibid.] 99: ‘Oh, geeminy, it’s him!’ exclaimed both boys.
1879		Sporting Times 15 Mar. 1/4: Erecting flats in North Bank — oh gemini!
1879		Yorkville Enquirer (SC) 27 Nov. 1/2: ‘Oh, geminy, what a durned ole fool’.
1890		Dead Bird (Sydney) 22 Mar. 6/4: Oh, gimmini, if that ain’t ’ot, goo blime.
1896		P.L. Dunbar ‘A Confidence’ in Lyrics of Lowly Life 175: All the fellers nudgin’ me, / An’ a-whisperin’, gemunee!
1899		‘Pot’ & ‘Swears’ Scarlet City 462: By Gemini! [...] what a high old time we might have had together.
1902		A. Bennett Grand Babylon Hotel 58: Gemini! By the beard of the prophet, it is!
1915		L.R. Dingus ‘A Word-List From Virginia’ in DN IV:iii 183: gee-miny, interj.
1922		Joyce Ulysses 405: Gemini, he’s going to holler.
1945		N. Marsh Died in the Wool (1963) 192: ‘Gemini!’ ‘I beg pardon, Mr Allen?’.