Green’s Dictionary of Slang

1. a general form of address to a man or woman one knows.

1853		N.Y. Clipper 20 Aug. 3/2: ‘Now he's got her! Give her h—II, old top’.
1866		Night Side of N.Y. 78: ‘How do you get along, old top?’ said his friend.
1866		H.L. Williams N.-Y. After Dark 78: Good bye, old tops!
1887		G. Devol Forty Years a Gambler 244: Come on, old top, and join me in a drink.
1911		E. Ferber Dawn O’Hara (1925) 105: I’m some rejoiced m’self, old top.
1914		H. Hershfield Abie the Agent 8 Dec. [synd. cartoon strip] Why should I be sore Van old topper.
1919		‘Sapper’ Mufti 92: Splendid, dear old top [...] let’s have a spot to celebrate your lapse from virtue.
1924		H.L. Wilson Professor How Could You! 139: Hello, old top.
1931		R.E. Howard ‘Blow the Chinks Down’ Action Stories Oct. 🌐 Rights vested in me by the Chinese government, working with the British authorities, old topper.
1936		(con. 1920s) Dos Passos Big Money (1966) 793: Hope it’s nothin’ serious, old top.
1945		G. Fairlie Capt. Bulldog Drummond 23: ‘Good health, Hugh.’ [...] ‘Skin off your nose, old top!’.
1953		R. Chandler Long Good-Bye 18: ‘How’s your drinking ?’ ‘Perfectly elegant, old top.’.
1976		L. Dawson The Spy Who Came... 83: ‘Don’t worry, old top’.

2. (S.Afr.) a father.

1986		P. Slabolepszy ‘Boo to the Moon’ in Mooi Street (1994) 116: You don’t know my Old Top. Only time the oke’s not got a glass in his hand’s when he’s at work.
1989		P. Slabolepszy ‘Smallholding’ in Mooi Street (1994) 178: Think you can take on your old top, hey? No, my boy.