Indeterminate means not known or decided. When someone contracts a rare stomach parasite but has not been traveling internationally, you might say it had indeterminate origins.
It's important to distinguish indeterminate from undetermined, which means not yet decided. When you buy an antique vase and don't know when it dates from, you might describe it as of an indeterminate era. If you are traveling and don't know when you plan to return home, you could say that your return is as yet undetermined.