In what sport were players originally nicknamed “leatherheads”?

Question: In what sport were players originally nicknamed “leatherheads”?

Options:

---

Correct answer:

More games: guess the idiom answers, infinite pics,  guess the emoji answers.

7 little words

1. Two-door Plymouth model
2. Bruise around the eye
3. Roosting rod 7 Little Words
4. Easy mark 7 Little Words
5. Hockey footwear 7 Little Words
6. Hairstyle 7 Little Words
7. Painter Jackson 7 Little Words
8. 1940s Fairey aeroplane
9. Kind of gull 7 Little Words
10. Insignificant person 7 Little Words