to distribute or allocate proportionally; divide and assign according to some rule of proportional distribution: to apportion expenses among the three men.
Origin: 1565–75; < Middle Frenchapportionner, equivalent to ap-ap-1 + portionner to portion
1570s, from M.Fr. apportionner, from O.Fr. aporcioner, from a- "to" + portioner "to divide into portions," from portion "share, portion" (see portion). Apportionment is attested from 1620s.