costume

Borrowed from French costume, which came from Italian costume, tracing back to Latin consuētūdō, meaning 'custom, habit.' It shares this Latin root with consuetude, custom, and kastom.

The word entered English as a noun for dress and appearance. Around 1802, it also began to be used as a verb, likely modeled on the French verb costumer, meaning to dress someone in appropriate attire.

It's a doublet of the English words consuetude and custom, all descending from the same Latin word for habit — so dressing up and doing things 'as usual' share deep roots.