In BTS song Mic Drop ft. Desiigner, the English part says "Did you see my bag? Do you see my bag? It's hella trophies and it's hella thick". They are referring that since they work hard their bag contain lots of trophies and it's heavy (thick). Since the original version is in Korean, when they sang that part in English it was funny so many people made it into a inside joke.
Commonly used to describe someone who is attractive and has an aesthetically pleasing lower back/behind.
Also a lyric in Mic Drop 'I got hella trophies and is hella thick'
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.