Meaning

noun a movable iron plate that regulates the draft in a stove or chimney or furnace

noun a device that decreases the amplitude of electronic, mechanical, acoustical, or aerodynamic oscillations

noun a depressing restraint

originFrom damp (verb) + -er. The name of the type of bread is first attested in 1825, and originally likely refers to damping the appetite.

Etymology from Wiktionary, CC BY-SA 3.0