J.K. Rowling called non-magical people in the wizarding world “Muggles.”
The term appears throughout the Harry Potter books for people who have no magical ability. Harry’s aunt and uncle, Vernon and Petunia Dursley, are Muggles, while Hermione Granger is a witch born to Muggle parents. This distinction allows the books to explore relationships between magical and non-magical communities.
“Squib” means something different: a person born into a magical family who cannot perform magic. “Mudblood” is an insulting term for a Muggle-born witch or wizard, so it is not a general synonym for Muggle. In the United States editions, non-magical people are also called “No-Majs,” especially in the Fantastic Beasts films.
Rowling has said the word was inspired by “mug,” an informal English term for a foolish or gullible person. The fictional meaning became widely recognized beyond the novels and entered broader popular usage for someone unfamiliar with a particular technology or activity.