Garb is not a costume, Garb is my preferred attire. My Garb is usually a kilt, a breacan feile if the weather's not too warm because I'm aiming at the late 16th century. If I must, I'll stretch the era a little and wear the philabeg as the shop I work at is in a vale and the air gets stagnant rather quickly.

A costume is something we wear to convey an altered image of ourselves.

"Appropriate Business Attire" is a costume.