Gnome trainers are rather unfriendly gnomes that shout insults at players training agility at the agility course in the Tree Gnome Stronghold such as "My granny is faster than you!" When talked to the gnome trainer will say "I'm amazed by how much humans chat. The sign over there says training area, not pointless conversation area."
The insults starting at the netting are "That's it, straight up", "Come on scaredy cat get across that rope", "My granny can move faster than you", and "move it, move it, move it!". In a hidden update the one closest to the net says "A terror bird can climb better than you!" when accessing the Advanced course. He also prevents you from proceeding onto the Advanced course without the required level.
You can also ask the gnome trainer your progress on getting agile legs.