Origin and history of yod

"very small amount," 1630s, figurative use of iota, ninth and smallest letter in the Greek alphabet (corresponding to Latin -i-). Its use in this sense is after Matthew v.18 (see jot (n.), which is the earlier form of the name in English), but iota in classical Greek also was proverbially used of anything very small. The letter name is from Semitic (compare Phoenician and Hebrew yodh).

"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.