early 15c., "to enlarge, expand, increase," from Old French amplifier (15c.), from Latin amplificare "to enlarge," from amplus "large" (see ample) + combining form of facere "to make, do" (from PIE root *dhe- "to set, put"). The meaning "augment in volume or amount" is from 1570s. The restriction of use to sound seems to have emerged from c. 1915 in reference to radio technology.
updated on September 20, 2022