Here are langauges that are from magical creatures that are in the books:
*Fairy - (fairies use a form of buzzing to communicate with themselves) *Gobbledegook - (goblin language) "bladvak" means "axe" in Gobbledegook (GF24) *Mermish - (merfolk language used above water; Merfolk speak human languages under the water)
*Parseltongue - (snake; it is a hissing sound) *Troll - ("Anyone can speak Troll. All you have to do is point and grunt.." - Fred Weasely)