A mother gives her child a nighty night kiss.
Nighty-night is defined as a baby-talk word that means "good night."
An example of nighty night is what you might say to your son as you tuck him into bed.
Informal good night
Origin of nighty-nightreduplicated, reduplication
Variant of night-night.
Origin of nighty-nightReduplication of night + -y3.
- (colloquial, usually childish) Alternative spelling of nighty night.
- (colloquial, usually childish) Good night.