If it isn’t AI (geeze have to question everything now), I would hazard a guess that it could be various injuries from textile machines or something.
It could also be just standard “major ouchies incurred as children” but grew back oddly due to lack of access to medical care.
This image has been around a long time, it’s not AI. The girls are (IIRC) oyster shuckers. So hand injuries are gonna be a thing.