The word yeet first rose to popularity as the name of a viral dance on social short video platform Vine in February 2014. It looks like the word started getting used as a general interjection of excitement in the next two months, including two viral videos involving throwing things while yelling “yeet”. The second, uploaded in April 2014 (archived on YouTube here), looks to be what solidified the association with throwing.

Unusually, the word died down along with Vine itself before experiencing a resurgence (not along with Vine itself) in 2018, now more established as a verb for “throw suddenly”. Google Trends