Posh, meaning fetch, or in otherwords, for you wookie smugglers, cool. It came from sewa, one day at camp looking up at the ceiling and her friend asking the question i will illustrate for you below.
Fetch, being another word for posh. Is used as a way to tell people they are the best, or cool, or "posh". Taken as a 'high compliment' when someone specific says it.
"That's a fetch watch, Sally!"
"Your boyfriend is fetch! You are so lucky!"