an old-timey or folksy way to refer to an injured or maimed lower extremity, usually as an excuse for not completing or participating in an activity
"Hey Paladia, wanna come out to the bop and show off your mad old school hiphop skillz?"
"Sorry Ender, I can't go dancing now. Ever since that boating accident I've got this bum leg..."
"That Aatif is such an asshole! Why doesn't he offer to help me carry the tequila bottles home?"
"Jane, you ignorant slut! It's not his fault he has a bum leg."