The story
Various: * (adjective) from un- (“not”) + potty trained (“able to use a children's potty or a full-sized toilet, having been through toilet training; continent”, adjective). * (noun) un- (“inverse of a specified action”) + potty training (“the act of weaning a child off of diapers and teaching them how to use a potty”, noun). * (verb) un- (“inverse of a specified action”) + potty train (“to train (a child) to use the toilet”, verb).
Etymology from Wiktionary, CC BY-SA 4.0.