What is the proper name for a tongue twister?

There isn't a more "proper" name for a tongue twister than tongue twister itself. It's the most commonly used and widely understood term.

However, you might encounter other variations like:

* Logorrhea (meaning "excessive talkativeness" but sometimes used to refer to tongue twisters)

* Alliteration (specifically referring to tongue twisters that use repeated consonant sounds)

* Verbal gymnastics (a more poetic and figurative term)

But ultimately, "tongue twister" is the standard and most appropriate name.