stamp (v.) Look up stamp at Dictionary.com
Old English stempan "to pound in a mortar," from Proto-Germanic *stamp- (cognates: Old Norse stappa, Danish stampe, Middle Dutch stampen, Old High German stampfon, German stampfen "to stamp with the foot, beat, pound," German Stampfe "pestle"), from nasalized form of PIE root *stebh- "to support, place firmly on" (cognates: Greek stembein "to trample, misuse;" see staff (n.)). The vowel altered in Middle English, perhaps by influence of Scandinavian forms.

Sense of "strike the foot forcibly downwards" is from mid-14c. The meaning "impress or mark (something) with a die" is first recorded 1550s. Italian stampa "stamp, impression," Spanish estampar "to stamp, print," French étamper (13c., Old French estamper) "to stamp, impress" are Germanic loan-words. Related: Stamped; stamping. To stamp out originally was "extinguish a fire by stamping on it;" attested from 1851 in the figurative sense. Stamping ground "one's particular territory" (1821) is from the notion of animals. A stamped addressed envelope (1873) was one you enclosed in a letter to speed or elicit a reply.
stamp (n.) Look up stamp at Dictionary.com
mid-15c., "instrument for crushing, stamping tool," from stamp (v.). Especially "instrument for making impressions" (1570s). Meaning "downward thrust or blow with the foot, act of stamping" is from 1580s. Sense of "official mark or imprint" (to certify that duty has been paid on what has been printed or written) dates from 1540s; transferred 1837 to designed, pre-printed adhesive labels issued by governments to serve the same purpose as impressed stamps. German Stempel "rubber stamp, brand, postmark" represents a diminutive form. Stamp-collecting is from 1862 (compare philately).