mid-14c., "musical sound or note," from Old French ton "musical sound, speech, words" (13c.) and directly from Latin tonus "a sound, tone, accent," literally "stretching" (in Medieval Latin, a term peculiar to music), from Greek tonos "vocal pitch, raising of voice, accent, key in music," originally "a stretching, tightening, taut string," which is related to teinein "to stretch" (from PIE root *ten- "to stretch").

The sense of "manner of speaking" is from c. 1600. In reference to firmness of body, from 1660s. As "prevailing state of manners" from 1735; as "style in speaking or writing which reveals attitude" from 1765. Tone-deaf is by 1880; tone-poem by 1845.

"to impart tone to," 1811, from tone (n.). Related: Toned; toning. To tone (something) down originally was in painting (1831); general sense of "reduce, moderate" is by 1847.

1888, agent noun from tone (v.). As a photography chemical, from 1920; in xerography, from 1954.

1779 of musical pitch; 1807 of persons, "having high moral principles; dignified," from high (adv.) + tone (v.).

"prevailing mode, style, fashionable ways," 1769, from French ton (see tone (n.)).

"of a high tone, affecting social elegance," 1877, American English slang, from tone (n.) + -y (2). It was the name of a reddish-brown fashion color in the 1920s.

in the musical sense, 1760, short for tonic note, from tone (n.) in the musical sense + -ic. Related: Tonicity.

1762, "low or subdued tone," from under + tone (n.). Figurative sense of "undercurrent of feelings, etc.," is attested from 1861.

1776; from tone (n.) in the musical sense + -al (1), or from Medieval Latin tonalis.

early 14c., "a musical sound," unexplained variant of tone (n.). From late 14c. as "a well-rounded succession of musical notes, an air, melody." Meaning "state of being in proper pitch" is from mid-15c.