means The gauge that displays how fast your vehicle is currently traveling, usually in miles or kilometers per hour.

from A straightforward 20th-century mash-up of "speed" — from Old English "sped," which once meant success or prosperity before it narrowed to mere swiftness — and "-meter," the measuring suffix from Greek "metron," a measure. The word arrived alongside the automobile, joining a whole family of "-meter" instruments (thermometer, barometer) that promised to put a number on the world.