Sounds as Interjections

There are certain words or sounds – some of them easier to pro­nounce than to spell – which may be classified as interjections. To mention a few:

Бррр!	Brrrr!
Тьфу!	Faugh!
Угу (pronounced with the mouth closed)	Yes
У-у (pronounced with the mouth closed)	No
Гм	Hum, Ahem
Хм	Humph
Кхе-кхе	Ahem (cough)
Апчхи!	Atchoo!
Цыц!	shut up
Тссс, Тччч	Shhh, Hush
Мммм...	Emm...
Хух! Фух!	Phew! (tiredness or relief)

These "words" are undoubtedly many milleniums old and probably the oldest in the language – going back to the days of Primitive Man.