Pronunciation
Etymology
() Apparently from the longer childish playground taunt sung to a tune particular to the taunt:
:I'm better than you,
:na-na, na-na, boo-boo,
:stick your head in doo-doo.
Na-na and boo-boo may be imitations of sounds a baby or young toddler might make.
Boo-boo may also indicate boo-boo, a very minor injury of a child such as a scraped knee.