jot (n.)

"the least part of anything," 1520s, from Latin iota, from Greek iota "the letter -i-," the smallest letter in the Greek alphabet, also "the least part of anything" (see iota). Usually (and originally) with tittle, from Matthew v.18.

"to make a short note of, set down quickly in writing or drawing," 1721, apparently from jot (n.) on the notion of a brief note or sketch. Related: Jotted; jotting.