The country of origin is the country you come from. In general, it is the country of nationality.
For some expatriates who acquire another nationality, their country of origin will be that of their “1st” nationality. Nowadays, more and more people have several nationalities, if it is allowed by the concerned countries. In this case, people usually tend to use the one which best fits their needs.
At Mondassur, for an international healthcare insurance quote, you need to indicate your country of origin and your country of destination.