Barooooo! is an achievement that is unlocked by adopting a baby yak.

While killing yaks, a very rare drop appears: a baby Fremennik yak. The chatbox message: A baby yak starts baroo-ing.

After picking it up, the chatbox message:

You pick up the recently orphaned baby yak.

Congratulations! You have completed: 'Barooooo!'. (Adopt a baby yak.)