Do you know what is the Hebrew name for the hand gesture (the two thumbs touching, the index fingers also touching, with the index and middle held together separated from the ring and little finger, also held together)?
I heard Leonard Nimoy say they got the idea of the Vulcan salute from this gesture, used in orthodox circles. Other people say it's the blessing for the congregation which only the high priest can do. A friend from Tureky says it's a kabbalistic blessing...
Thanks for your question.
The following excerpt and chapter-note from my book, "The Synagogue Survival Kit," is taken from the section describing the decorative motifs one might encounter in a synagogue.
Another common decorative motif is a hand, with a wide spread between the middle and ring fingers; or a pair of such hands. This is the ancient handsign of the ko-ha-nim (priests) in the Temple. The priestly handsign is symbolic of divine immanence. The handsign was used by the kohanim when they pronounced The Priestly Blessing on the congregation. This ritual is still a part of the service, and is discussed later. This Jewish ritual has been popularized by the Star Trek TV show, which used it as the Vulcan ritual of greeting. The Vulcan ritual of greeting consists of the handsign accompanied by a blessing: "Live long and prosper," which is an abbreviated paraphrase of the original Jewish blessing.17 The modern Hebrew greeting ("Shalom") is a still shorter version of this blessing.
17 Star Trek's use of the Jewish ritual is not coincidental. Leonard Nimoy, the actor that portrayed the original Vulcan, Mr. Spock, got his first acting jobs in Yiddish Theater, and has been Baal Koreh (Torah reader) at his synagogue.
Birkat Kohanim (The Priestly Blessing) is also called duchening, as though there were an English verb "to duchen". This ritual is discussed extensively in the section of my book describing the structure of the Amidah. The commandment to duchen, and the text of the blessing, is found at Numbers 6:23-27. It is done during the repetition of the Amidah, just before Sim Shalom. It includes ritual handwashing of the kohanim by the levites. This is done privately after the K'dushah and before Modim -- after the kohanim have removed their shoes (or loosened their laces so as not to touch their shoes again). Then the (now shoeless) kohanim ascend the bima. There is a public benediction by the kohanim before they perform the mitzvah, the blessing itself, and accompanying meditations. All kohanim (descendents of Aharon) present in the synagogue participate in the duchening and make the "kohanic" handsign. Their taleisim are pulled way forward over their heads so as to cover their raised hands. Also, the congregation often does the same, and in any case does not look at the duchening. Ashkenazim duchen only on major holidays, while Sephardim duchen frequently. (Reform congregations are an exception. They generally do not recite The Priestly Blessing.)