Green’s Dictionary of Slang

1. mistaken, inept, prone to error.

1957		‘Ed Lacy’ Lead With Your Left (1958) 154: You had a wrongo hunch on that.
1968		K. Brasselle Cannibals 88: A bad love affair, wrongo marriage, poverty, career.

2. unpleasant, undesirable.

1953		T. Runyon In For Life 245: Wrongo convicts and no-good guards seldom received shoes deliberately manufactured to be painful.
1956		T. Thursday ‘The Big Squawk’ in Smashing Detective Mag. 15 Apr. 🌐 When you are dealing with a wrongo guy, you gotta beat the bum to the punch.