This one isn’t as common as the others, but it’s still used in certain areas and is featured here mainly because I think it’s funny and interesting. “Su merced” literally means “your mercy”, sort of the Spanish equivalent of the antiquated form of address in English of “your grace”. “Merced” means “mercy”, “su” in this context means “your”. “Su” is the formal, 2nd person possessive, what you would use to say “your” when speaking to someone you would refer to as “usted”: “su merced” = “la merced de usted”. Variations of this include “su mercé” and “vuestra merced” (very uncommon).
It’s an especially polite form of address having evolved over the years to be used in the way English speakers might use “sir” and “ma’am/madam”. It sounds very funny to most native Spanish speakers (see below video of a Panamanian newscaster talking about having heard it on a recent trip to Colombia) and, outside of the few localities in which it is still in common use, would absolutely seem overly formal (in other words, don’t use it, but now you know what it is on the off chance you hear it).
It’s not in particularly common use anymore outside of a few, more rural departments of Colombia (particularly the less-populated areas of Cundinamarca and Boyacá). If your Spanish is decent there’s a wiki article specifically on the dialect of Spanish spoken there. I’ve spoken with people from Bogota about this who have told me their grandparents would use these terms as well, so even in cities like Bogota you may occasionally hear it used by more elderly people.
I learned to speak conversational Spanish in six months using TV shows, movies, and even comics: I then wrote a book on how you can, too
I have a whole method and a book I wrote about it called The Telenovela Method where I teach you how to learn Spanish from popular media like TV shows, movies, music, books, etc. that you can all find online for free. It was the #1 new release in the Spanish Language Instruction section on Amazon for nearly a month after it came out and currently has 17 reviews there with a 4.9/5 stars average. It's available for $7.99-$9.99 for the e-book version depending on who you buy it from (Kindle version on Amazon is now $7.99) and $16.99 for the paperback (occasionally a bit cheaper, again, depending on who you buy it from).
It's currently available in both e-book and paperback from: