the.com/slumber party

means A gathering where kids or teens spend the night at someone's house, staying up late with snacks, games, and talk.

from A straightforward compound — 'slumber,' from Old English-rooted words for sleep that passed through Middle English, plus 'party' in its sense of a festive social gathering, a sense that solidified in English by the 17th-18th centuries. The phrase itself is a 20th-century American coinage, rising alongside suburban childhood culture and sleepover traditions; it names the occasion ironically, since the whole point was staying awake.