Like many words 'shoe' starts to sound odd if you say it for a while, it starts to shuffle along like slippers, leave meaning's room, shooed out, showing signs of wear and tear, as the open 'oe's fade to leave the 'sh'.  And saying that suggests some conflation between the foot's sole and and toe, to make up the outer casing, the second skin, of skins, that sometimes stand around alone, in  pairs.