The word 'whoop' is an excellent example of onomatopoeia, where the form of the word imitates the sound it describes. It entered Middle English as 'whopen' or 'houpen', likely echoing the sound of a loud cry or shout. This imitative origin is shared with similar interjections across languages, capturing the abrupt, explosive quality of a yell. Over time, its application specialized in medical terminology to describe the characteristic gasping sound of 'whooping cough', directly linking the sound of the disease to the core meaning of the word.

This word is a simplex form, likely of imitative origin. It is not productively composed of smaller, independent morphemes in modern English.