means The particular quality, pitch, or character of a sound, voice, color, or attitude — the how that colors the what.

from From the Greek 'tonos,' meaning a stretching or tightening — literally the tension of a string. The Greeks heard pitch as a matter of how taut the cord was pulled, so the word for 'strain' became the word for 'sound.' It traveled through Latin 'tonus' into Old French and English, where it stretched even further: from musical pitch to color to the unmistakable strain in someone's voice that tells you exactly how much trouble you're in.