What in python slang means "dunder"?

Question

deep-under? dual-under? do you need her?

Answer 1

Double UNDERscore
such as __
__init__()

Answer 2

__thanks__()

Answer 3

Dunder or magic methods in Python are the methods having two prefix and suffix underscores in the method name. Dunder here means “Double Under (Underscores)”. These are commonly used for operator overloading. … These methods are the reason we can add two strings with '+' operator without any explicit typecasting.
See: https://slangsearch.org/