Football Players did not wear matching strips or team identifying jerseys until the very end of the 1800’s.
Although the first official international association football was played between England and Scotland in 1872, caps were not awarded at this time.
Caps were awarded for the first time at international level in 1886 (further details on the football national team page.)
The physical awarding of caps nowadays is not common place with caps being issued more for player milestone events. The phrase “Cap” remains in name only to signify an international qualifying game as deemed by the awarding football association.