Mhmm... Just a second after posting my answer I recognized that maybe there IS a bit of a meaning in the words "falleri, fallera".
The german word "fällen" means "to fell". And the song deals with a wood auction... So maybe the author tried to stylize the word "fällen" and made "falleri" out of it.
But nevertheless the words don't have a real meaning and are just meant to sound funny.