In his 1975 autobiography "I Am Not Spock", Nimoy, who was Jewish, wrote that he based it on the Priestly Blessing performed by Jewish Kohanim with both hands, thumb to thumb in this same position, representing the Hebrew letter Shin (ש), which has three upward strokes similar to the position of the thumb and fingers in the gesture. The letter Shin here stands for El Shaddai, meaning "Almighty (God)", as well as for Shekhinah and Shalom. Nimoy wrote that when he was a child, his grandfather took him to an Orthodox synagogue, where he saw the blessing performed and was impressed by it.