"dry measure of one-quarter bushel," late 13c., pekke, of unknown origin; perhaps connected with Old French pek, picot (13c.), also of unknown origin (Barnhart says these were borrowed from English). Chiefly of oats for horses; original sense may be "allowance" rather than a fixed measure, thus perhaps from peck (v.). Originally not a precise measure and later sometimes used colloquially as "a great deal" (a peck of troubles, etc.).