In the context, I think it's a sort of "fol-de-rol" or "too-ra-laye-ay". One could take it as a "here we go" kind of cry, but it wouldn't make sense with all the verses then.

I don't want to rain on anyone's parade, but as a Salonican myself I dislike the song; it's not how I want my town to be remembered. Tough shit, I suppose, but it caused me to write my "Memories of Salonica" as an antidote. Still, this is not the place for it.