Green’s Dictionary of Slang

’lo phr.

hello.

1925		D. Hammett ‘Tom, Dick, or Harry’ in Nightmare Town (2001) 244: ‘Hello, Jack!’ Phyllis greeted the prisoner. ‘’Lo, Phyl,’ he mumbled.
1933		J. Spenser Limey 19: ’Lo, Jack.
1943		J. Phelan Letters from the Big House 82: ‘’Lo, Nobby. ’Lo, Rowley,’ Kennion greeted them.
1951		D. Stivens Jimmy Brockett 47: ‘’Lo, Jimmy,’ he said. ‘I was going up to you’.
1957		H. Simmons Corner Boy 44: ’Lo, Monk.
1983		C. Heath A-Team 2 (1984) 171: ’Lo, Doc.