I usually use the nickname moebiusband. If you google for moebiusband you can read on Wikipedia (Quote from the Wikipedia article):

A Möbius strip is a surface with only one side (when embedded in three-dimensional Euclidean space) and only one boundary. Its discovery is attributed to the German mathematicians Johann Benedict Listing and then independently August Ferdinand Möbius in 1858.

A Möbius strip made with a piece of paper and tape. (By David Benbennick - Own work, CC BY-SA 3.0, Link to original):