Guest above is refering the the "Year King" motif in mythology.

Wikipedia has quite a good entry on the subject as does the Fantasy Encyclopedia. the latter refers to The Year King theme in literature. if you are at all interested in the fertility themes of the song, you'd enjoy reading about this.

Here's a link to Wikipedi'as article.

Sacred King/Year King

This topic has come up from time to time in threads, most recently in a discussion comparing the original WICKERMAN to the recent subpar remake which removes the Year King motif.