What is a "kata" in this context?

When I RTFA I see

YouTube - ‪String Calculator TDD Kata done in Perl‬‏

Kata idea by: Roy Osherove - http://osherove.com/tdd-kata-1/

The following is a TDD Kata- an exercise in coding, refactoring and test-first, that you should apply daily for at least 15 minutes (I do 30).

Kata appears to be a kata in this context :)