Bree-yark is most definitely not "I surrender" in the goblin language.
A foreign phrase that you tell someone means the opposite of what it actually means, in order that hilarity will ensue sometime later when they say it or hear it said.
In the
Original Dungeons & Dragons adventure module B2 "The Keep on the Boderlands", one of the random rumors that characters can be told upon starting the
adventure is that "'Bree-Yark!' is goblin-language for 'we surrender!". The DM, howerver, is told that it actually means "Hey, Rube!" and is a signal for any nearby goblins to come join in an attack.