bye-bye

bye-bye [interjection bahy-bahy; noun, adverb bahy-bahy] Word Origin interjection

1. Informal. goodbye.

noun

2. Baby Talk. sleep.

Idioms

3. go bye-bye, Baby Talk.
   1. to leave; depart; go out.
   2. to go to sleep; go to bed.

Origin of bye-bye 1700–10; apparently orig. nursery phrase used to lull a child to sleep, later construed as reduplicative form of bye, short for goodbye