1) From ‘balled’; that is having a white ‘ball’ or patch in the face, used of animals.
The examples can be divided into two groups, those with ‘ball’: 1539 his owne horse ... that had the ball in the hede, Tunstall
1558 a baye stagge with a ball in the face, Pontefract
1579 a blacke twynter whye with a ball in the head, Slaidburn and those with ‘bald’: 1434 my red bald stagg, Ousefleet
1507 my bald horse, Raventhorpe
1549 my balde maire, South Milford
1655 one bauld meare, Whitley. It almost certainly explains the name Ball given to horses: 1495 equum vocatum Ball, York
1772 Bawle my good old horse, Mirfield.