banana
Pronunciation: /bəˈnɑːnə/
noun

Phrases
-
go (or be) bananas
informal - become (or be) mad or extremely silly: everyone’s beginning to think I’m bananas
- become extremely angry or excited: she went bananas when I said I was going to leave the job
-
top (or second) banana
- informal the most (or second most) important person in an organization: a top banana of the Mafia

Origin:
late 16th century: via Portuguese or Spanish from Mande