What is "leatherheads"

n. (plural of leatherhead English)

Leatherheads is a 2008 American sports comedy film from Universal Pictures directed by and starring George Clooney. The film also stars Renée Zellweger, Jonathan Pryce, and John Krasinski and focuses on the early years of professional American football.

The script is by Duncan Brantley and ESPN's Rick Reilly.