I do my best to be polite to Alberto and Marietta when I am in Canedo at the bottom of the road. They are Portuguese but my starting point is schoolboy Spanish.
I tried gracias for thank you only to be politely corrected with what I heard as obligado, which I took on board following a connection to, say, much obliged in English.
Done a little research since. The word is actually obrigado and, here's the rub, it is gendered. You say obrigado if you are a man, and obrigada if you are a woman. I have never heard of such a thing before. I am familiar with gendered nouns in Romance languages but I would never have imagined that language might mutate based on the gender of the speaker.
One for J K Rowling to work out I think. Way above my pay grade.