means A liquid skincare product applied after cleansing to balance, refresh, or prep the skin (or, in printers, the fine powder that forms the printed image).

from From 'tone' plus the agent suffix '-er' — literally 'a thing that tones.' 'Tone' traces back through French and Latin 'tonus' to Greek 'tonos,' meaning tension or stretch (the same root behind 'tone' in music and muscle). The cosmetic sense leans on the idea of restoring or tightening the skin's 'tone'; the printer sense borrows the word for the powder that lays down image and shade.