NAWATL GLOSSARY
Masatsin. Yei's full name is Yei-Masatl Tlilxochitl, "3-Deer Vanilla." The word for vanilla, tlilxochitl, literally means "black flower," and is a compound of tlilli (ink) + xochitl (flower). Tliltik, the word for the color black, comes from the word tlilli, the word for ink.
For this story, their names work like this:
Yei-Masatl is his calendar name, given in accordance to day birth, and the name everyone uses. Tlilxochitl is the name his family gave him, and it's used only for family and very close people.
Here, his coworkers are also his friends, so they call him Masatsin: the suffix -tsin adds an affectionate meaning to the name. -Tsin also adds, in a more formal setting and in classical nahuatl, a form of respect.
(-Tsin is mostly used as an affectionate diminutive, similar to -ito in spanish. But let's keep the more classical and respectful use for names in this story, and the diminutive for animals and objects. In truth, it depends on who is saying it, and the intention.)
Nokniuh. My friend. Also can be my brother/sister. From No (my) + Ikniuh (friend, brother, sister).