User blog comment:GoDai/GoDai's Translations: People and Groups in the Tower (1)/@comment-4076672-20120627133154/@comment-1926430-20120627223158

Honestly, I'm not too sure either.

By inventory, I think SIU means like, the video-game kind of inventory. Considering how you say "inbentori" in Korean, it's probably meant to refer to the inventory used in RPG games like Maplestory, hence the bag where you put items in.

I think it does refer to the part where you wrap the reel around.

In that case, it seems most Arms Inventories are connected to Reel Inventories.