This is the 10326th most frequent Russian word.
бу
"Бу" in Russian is an interjection used to mimic a sudden scare or surprise, similar to "boo" in English.
The word 'бу' is used here as an interjection to mimic a sound used for startling someone.
Бу! Как же я испугалась.
Boo! How scared I was.
The word 'бу' is being repeated playfully, mimicking infantile or joyful sounds.
Малыш радостно кричал «Бу-бу!»
The baby cheerfully shouted 'Boo-boo!'
The word 'бу' is used again as an exclamation to startle or entertain participants.