A mark pressed on to certify or to date. A stamp says someone attested this.
Old English stempan (to pound, to crush underfoot), from Proto-Germanic *stampjan; the sense of certifying by a pressed mark grew from the plain act of pressing something down hard.
A mark pressed on to certify or to date. The word for pounding underfoot became the word for attesting, because both are a force applied once and left behind.