gaga

 
Pronunciation: /ˈgɑːgɑː, ˈgagə/

adjective

informal
  • slightly mad, typically as a result of old age, infatuation, or excessive enthusiasm.

Origin:

early 20th century: from French, 'senile, a senile person', reduplication based on gâteux, variant of gâteur, hospital slang in the sense 'bed-wetter'