A Boy Trunk on sale in a Cattlelog.
An Accessory Trunk is a furniture item used to hold Accessories. There are currently two types of trunks: a Boy Trunk and a Girl Trunk. They each cost 5 Jellybeans. Trunks appear to hold 50 accessories. It is possible to buy accessories without a trunk, but you won't be able to wear them until the trunk arrives.
Only boys can purchase the boy trunk and only girls can purchase the girl trunk.