1635-45; adj. use of obsolete noun: that which amounts to as much, itself noun use of obsolete v.: to amount to as much < Anglo-Frenchtant amunter or Italiantanto montare to amount to as much. See tanto, amount
1641, from verbal phrase tant amount "be equivalent" (1628), from Anglo-Fr. tant amunter "amount to as much" (1292), from O.Fr. tant "as much" (from L. tantus, from tam "so") + amonter "amount to, go up" (see amount).