- bare skin; nakedness: They were sunbathing in their birthday suits.
Origin of birthday suit
- informal, jocular a state of total nakedness, as at birth
Word Origin and History for birthday suit
first attested 1730s, but probably much older. The notion is the suit of clothes one was born in, i.e., no clothes at all. Cf. Middle English mother naked "naked as the day one was born;" Middle Dutch moeder naect, German mutternackt.
To be “in one's birthday suit” is to be completely naked (as people are at birth).
Idioms and Phrases with birthday suit
Nakedness, as in The doorbell rang, and here I was in my birthday suit. In 18th-century Britain this term originally referred to the clothes one wore on the king's birthday. Later it was jocularly transferred to bare skin, alluding to the condition of a newborn baby.