They're called the Five Ks because in the Punjabi language, they all begin with a K: kara - a steel bangle; kesh - uncut hair; kangha - a comb; kaacha - undershorts; and kirpan - a short sword.
Kirpan (symbolic dagger), kangha (comb) and kachcha (underwear) are the other three. There have hardly been any claims that Sikhs haven't been allowed to sport the five kakars in India.