Supermarkets in Israel now stock salt with added yod. No, they haven’t figured out a way to infuse a favourite condiment with the tenth letter of the Hebrew alphabet — yod refers to iodine.
How yod came to signify both a letter and a chemical is quite straightforward. Iodine derives from the Greek iota, the smallest letter in the Greek alphabet. Iota, in turn, comes from the Hebrew letter yod.
Whereas iota and its English cognate “jot” suggest a very little part or amount, Hebrew uses the saying “kutzo shel yod”, the little peak on the upper left corner of the letter.
People speak of the Torah containing not so much as a superfluous kutzo shel yod. Likewise, one should be loyal to the law down to the kutzo shel yod.
Influenced by the polemical poem Kutzo Shel Yod, by Haskalah (Enlightenment) poet Yehuda Leib Gordon, in which a fixation with legal details leads to cruelty, the expression can bear a negative connotation in modern Hebrew.
In Kabbalah, kutzo shel yod symbolises the first and highest level of Creation, a realm so ethereal that no one can grasp it. The yod itself symbolises the first sefirah of hochmah — knowledge, awaiting deciphering and implementation by the other sefirot.