3 letters:
cos, dos, ros, vis, von, vos

4 letters:
coss, doss, goss, joss, koss, loss, moss, noss, poss, soss, toss, valk, vase, vass, vaux, vess, vice, vise, vohs, vong, vore, yoss, zoss, voss

5 letters:
boss', fauss, knous, mauss, nauss, sauce, verse, voice, vorce

6 letters:
knauss, vaughn, vaught, vought

7 letters:
vaughan