microdot (n.)

word-forming element meaning "small in size or extent, microscopic; magnifying;" in science indicating a unit one millionth of the unit it is prefixed to; from Latinized form of mikros, Attic form of Greek smikros "small, little, petty, trivial, slight," perhaps from PIE *smika, from root *smik- "small" (source also of Old High German smahi "littleness"), but Beekes thinks it a Pre-Greek word.

"point or minute spot on a surface," Old English dott, once, "speck, head of a boil," perhaps related to Norwegian dot "lump, small knot," Dutch dot "knot, small bunch, wisp," Old High German tutta "nipple;" a word of uncertain etymology.

Known from a single source c. 1000; the word reappeared with modern meaning "mark" c. 1530; not common until 18c. Perhaps this is a different word imitative of "the mark of a mere touch with the pen" (Wedgwood). In music, the meaning "point indicating a note is to be lengthened by half" is by 1806. Morse telegraph sense is from 1838. On the dot "punctual" is 1909, in reference to a clock dial face. Dot-matrix in printing and screen display is attested by 1975.