installment Look up installment at Dictionary.com
"act of installing," 1589, from install. Meaning "arrangement of payment by fixed portions at fixed times" is from 1732, alteration of Anglo-Norm. estaler "fix payments," from O.Fr. estal "fixed position," from O.H.G. stal "standing place." Fig. sense of "part of a whole produced in advance of the rest" is from 1823.