In finance and economics this term is used to allude to small savers, who due to their very little finanacial literacy expose themselves to the risk of investing in junk bonds or cryptocurrencies and lose a great chunk of their savings. So, like oxen that are gonna be slaughtered. In the movie "Trading places" (starring Eddie Murphy) there is an ox park scene at the end of the movie where everyone does just like the others (illiterate in terms of finance) do and loses money basically. It describes a herd of cattle on the range unaware they're going to be slaughtered.
Ox park has lost dough by investing in Bitcoin and in Venezuela and Greece government bonds