munchkin
A cute nickname for a small child.
A munchkin is an affectionate nickname for a small child, emphasizing their cute, tiny size. Parents might call their toddler a munchkin while scooping them up for a hug, or a teacher might refer to her kindergarten class as “my little munchkins.” The word carries warmth and fondness, like calling someone a “little one” or “kiddo.”
The term comes from The Wizard of Oz, where the Munchkins are the small, friendly people who live in the colorful land where Dorothy's house lands. In the 1939 movie, they're famous for singing “Ding-Dong! The Witch is Dead” in high, cheerful voices. Their small stature and sweet nature made “munchkin” a natural term of endearment for young children.
You'll also encounter munchkin as the name of a cat breed with very short legs, bred to look perpetually kitten-like. Some people use it playfully for anyone noticeably shorter than average, though this can feel less affectionate if you're the one being called it. When your grandmother calls you her “little munchkin,” though, she's simply showing how precious you are to her.