Green’s Dictionary of Slang

(US) a taxi-driver.

1938		R. Chandler ‘Red Wind’ in Red Wind (1946) 30: A hacker asleep in his cab.
1941		J.K. Butler ‘Saint in Silver’ in Goulart (1967) 60: It’s the custom of hackers to ring the office.
1945		R.L. Bellem ‘Coffin for a Coward’ in Hollywood Detective Dec. 🌐 I flagged a cruising Yellow, piled into it, told the hacker where I wanted to go.
1961		‘Lou Rand’ Gay Detective (2003) 92: ‘Where to, Mac?’ asked the hacker.