1526, borrowing of L. jota, variant spelling of Gk. iota "the letter -i-, the smallest letter in the alphabet, hence the least part of anything. The verb "to make a short note of" is attested from 1721.
or Iota, the smallest letter of the Greek alphabet, used metaphorically or proverbially for the smallest thing (Matt. 5:18); or it may be = yod, which is the smallest of the Hebrew letters.