Webster’s Revised Unabridged Dictionary · 1913
Coss
Coss (kŏs), n. [Cf. Pers. kōs a road measure of about two miles; or Skr. krōça.] A Hindoo measure of distance, varying from one and a half to two English miles. Whitworth.
Coss, n. [It. cosa.] A thing (only in phrase below).
Rule of Coss, an old name for Algebra. [It. regola di cosa rule of thing, the unknown quantity being called the cosa, or the thing.]