英语词源字典 - 在线词源网站

amplitude (n.)[amplitude 词源字典]: 1540s, from Middle French amplitude or directly from Latin amplitudinem (nominative amplitudo) "wide extent, width," from amplus (see ample). Amplitude modulation in reference to radio wave broadcast (as opposed to frequency modulation) first attested 1921, usually abbreviated A.M.[amplitude etymology, amplitude origin, 英语词源]
frequency (n.): 1550s, "state of being crowded" (now obsolete); 1640s, "fact of occurring often;" from Latin frequentia "an assembling in great numbers, a crowding; crowd, multitude, throng," from frequentem (see frequent). Sense in physics, "rate of recurrence," especially of a vibration, is from 1831. In radio electronics, frequency modulation (1922, abbreviated F.M.) as a system of broadcasting is distinguished from amplitude modulation (or A.M.).