c.1300, "an ordinance to fix the amount of a payment or tax," from O.Fr. sise,
shortened form of assise
"session, assessment, regulation, manner" (see assize
), probably a misdivision of l'assise
as la sise
. The sense of "extent, amount, magnitude" (c.1400) is from the notion of regulating something by fixing the amount of it (weights, food portions, etc.). Specific sense of "set of dimensions of an article of clothing or shoe" is attested from 1591. Sizeable
"fairly large" is recorded from 1613.