Business shirt underpants (n.) 

ツナギシャツ

A business shirt and a pair of underpants joined to form one clothes garment sold only in Japan. Often worn by women, sometimes worn by district court judges.

E.g. A new pair of business shirt underpants were lying in the real estate agent’s chest of drawers unused for over a month.

– New Wasabi Dictionary: A Dictionary for Gaijin, 1st Edition, TRW (The Rising Wasabi)