だて [date] – Date was originally a proper name. Nowadays it’s more commonly used to mean “for show-off.” For example, 伊達眼鏡 [date megane] are glasses that one does not actually need, but wears anyway for aesthetic reasons.
How did this come to be? For one thing, it sounds similar to 立て [tate], which can mean something like ‘propping up’ or ‘supporting’.
Another factor is that it probably started off as a kind of joke poking fun at the attire of the historically prominent Date family, who were lords of the present-day Sendai area throughout the Edo period.