Green’s Dictionary of Slang

(US) innocent, novice.

1899		Sat Eve. Post 1 July 3: [of a novice railroad engineer] What’ll she do to this chippy runner [HDAS].
1926		J. Black You Can’t Win (2000) 94: Didn’t him and Smiler bring it up here to me for my end of that chippy gambling house’s bankroll.
1941		‘Digg Mee’ ‘Observation Post’ in N.Y. Age 19 July 9/7: That certain married woman and her escapades (dangerous!) with the chippie boys.