The lyrics are designed to evoke a feeling, but not confuse the player with actual lyrics they might understand (especially if the song is playing while characters are talking in-game).

To do this, the songwriter just created nonsense words that made the sound they wanted, and later on called it Chaos Language. That way they only had to record the song once for all localizations. Its not a real language though, because it doesn’t have any grammar rules or anything.

They did sing some songs in multiple real languages though, which typically play during the end credits.