gussy up /ˈætɪtuːd/ (n): 

#​ [gussy up | gussy somebody/something up] (North American English, informal) to dress yourself in an attractive way; to make somebody/ something more attractive, especially in a showy way.

SYNONYM dress up;

Even the stars get tired of gussying up for the awards.


go commando /kəˈmɑːndəʊ/ /kəˈmændəʊ/ (idiom): 

# (informal, humorous) to not wear underwear under your clothes.


habit 

# [countable] a long piece of clothing worn by a monk or nun.


lingerie /ˈlɒ̃ʒəri/ or /ˌlɑːndʒəˈreɪ/ (n):

# (used especially by shops/ stores) women’s underwear.