It stems from gaming community. They started referring to it as the tilde key because the accent grave, accent de major, back tick, opening single quote, and about 13 other names for the unshifted tilde made it difficult to communicate to others. So, yes, technically speaking the tilde key(using shift) puts you into walk mode by default, and the accent grave gives you the pie menu(view pie by default). Side note: it is always to the left of number 1 on top row on a standard qwerty keyboard.
