Etymology Clipping of Walter. The derogatory British sense is a reference to the fictional character Walter Mitty from The Secret Life of Walter Mitty, a mild-mannered pushover who has wild fantasies about his life in various daring roles.
Etymology From Middle English walten, from Old English wæltan, weltan, wieltan, wyltan, wiltan, from Proto-West Germanic *waltijan, from Proto-Germanic *waltijaną (“to roll; roll about”), from Proto-Indo-European *wel- (“to turn; wind; twist”). Cognate with German wälzen (“to wallow; roll”), Danish vælte (“to tumble; overthrow”), Swedish välta (“to roll; tumble over; overthrow”). Related to waltz.
Etymology From Middle English *walt, from Old English *wealt (attested in unwealt (“not given to roll; steady”), sinwealt (“circular, eternally rolling”)), from Proto-Germanic *waltaz (“changing; unstable”), from Proto-Indo-European *wel- (“to turn; wind; twist”).