Leonard Nimoy, in his autobiography
I Am Spock, says this sign was originally a sign of Jewish blessing, resembling the Hebrew letter Shin.
http://en.wikipedia.org/wiki/Vulcan_salute
As for the lines, they have been interpreted as a cross, or a Saturn sign, among other things.
I would like to suggest that the meaning is a bit more complex and mysterious, yet also simple. In the book,
Hands -A Complete Guide to Palmistry; Whitford Press; 1983; Page 188, Enid Hoffman talks about "ambition lines." These are lines that extend from, but never cross, the "life" line. They indicate the presence of ambition in whatever direction they point to. In the earliest US Games RWS decks and the "Pam A,"
http://learntarot.com/bigjpgs/maj15.jpg
http://www.sacred-texts.com/tarot/pkt/img/ar15.jpg
what we see are ambition lines extending from the life line and wrapping around the "head" line. The way I interpret this is it is illustrating that a good portion of The Devil's life energy is being channeled into intellectual activity, even to the point of bondage.
In the Book of T Tarot, The Devil becomes the Thinker. From the book,
T -The New Tarot: The Tarot for the Aquarian Age; Western Star Press; 1969; Page 58, Rosalind Sharpe and John Cooke make this observation:
"The old Tarot trump which this Book (tarot card) replaces was called Satan, or The Devil. Actually, the thinking brain is that which gets man into the state termed hell. It is what binds man. Hence, formerly the man and woman were chained to Satan's goat feet or to the throne on which he sat. The Satan card was read as sex. But sex is not the cause of man's dilemma. It is a man's thinking about sex that enslaves him."
While the book shows its age by the constant use of "man" and "a man's," the message is clear. I added the (tarot card) part.