The word "oof" is a colloquial term used in various contexts, but it often refers to a sound made when something heavy falls or strikes something else, or sometimes used as an expression of discomfort or surprise. It is largely informal and may not be widely recognized as standard English.
The etymology of "oof" is not well-documented, as it appears to be a slang term that could have originated in various informal contexts. It might be an onomatopoeic word, mimicking the sounds associated with impacts or heavy falls.