In Martin Scorsese's movie Cape Fear (1991) Cady has a brief exchange with a PI hired by Sam Bowden
Cady: Are you my friend?
PI: No, I'm not your friend.
Cady: Oh. 'Cause I thought maybe you were my friend, because I like to plan my comings and goings with friends. But if you're not my friend, and you're planning my comings and goings, I'd call that presumptuous. In fact, I'd call it downright rude, because I ain't your porch-baby, buddy.
The first half of Cady's line is pretty easy to understand. What does he say "I ain't your porch-baby"? I am not sure if he is being menacing with that line.