Lyric discussion by falcotron 

Cover art for X, Y, & Zee lyrics by Pop Will Eat Itself

"X, Y, and Zee" is a 1972 British movie that's mostly famous for the Liz Taylor/Susannah York/Michael Caine threesome.

It's also the alternate name for the movie's theme song, also titled "Going in Circles", which became more famous when it was covered by Three Dog Night.

I don't think the PWEI song has anything to do with either; I think they just liked the title, which conjures up impressions of threes, and of the end of everything, and of non-Britishness ("zee" rather than "zed").