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early 15c., "to enlarge or expand," from Middle French amplifier, from Latin amplificare "to enlarge," from amplificus "splendid," from amplus "large" (see ample) + the root of facere "make, do" (see factitious). Meaning "augment in volume or amount" is from 1570s. Restriction of use to sound seems to have emerged in the electronic age, c.1915, in reference to radio technology.