This theory suggests that the original meaning the sword came from 'Hebi no Tsurugi' ('hebi' for 'serpent' and 'tsurugi' for 'sword), with 'kusa' (grass) referring to 'smell' and 'nagi' referring to 'snake' (see names of 'unagi' (eels)).
クサは臭、ナギは蛇の意（ウナギ名前などを参照）で、原義は「蛇の剣」であるという説。