The "K" in names of radio stations

Hi all! I´ve asked some american people this before, but nobody seems to know the answer (is there any?): What does the K stand for in the names of radio stations. In movies and on TV when the name of a radio station is mentioned it always seems to have the letter K in it. Often a W also. KW-RockFM or someting. Not to many words in english starts with the letter K, and I just can´t figure it out. Anyone?

Here’s what The Master has to say about this.

There was also additional information provided on this MB in the infelicitously named Cecil’s Lousy Call Letter Answer (repost) thread.