the.com/backflip

means An acrobatic move where you rotate your whole body backward through a full circle in the air, landing on your feet.

from A straightforward compound of 'back' (the direction of rotation) and 'flip' (to turn over quickly), with 'flip' itself likely echoing the light, snapping sound of something turning suddenly — related to words like 'flick' and 'fillip.' The move predates the word's gymnastic use by millennia, but the term as we use it for the acrobatic trick is a modern, plainly descriptive coinage, no mystery required.