Okay, I kind of get it. One because people in Indonesia (neighbouring country) seem to eat all the time. And two because there's merenda in Italian for a snack which falls between meals ... for example what kids eat when they come home from school. Presumably merienda is the Spanish equivalent thereof.
An extra meal in the Philippines that falls between lunch and dinner. I haven't figured out yet if the extra meal between breakfast and lunch has its own name or is also a form of merienda. (Yes, we were actually served five meals one day, including a blowout.)