The original goat pentagram containing the Hebrew letters at the five points of the pentagram spelling out Leviathan (לויתן) first appeared in the book La Clef de la Magie Noire by French occultist Stanislas de Guaita, in 1897. This symbol was later used in Maurice Bessy's book A Pictorial History of Magic and the Supernatural[8], with the words "Samael" and "Lilith" removed. During his years of research into the “black arts”, LaVey had come across this book and added it to his collection. When he chose to turn his magic circle, the Order of the Trapezoid, into the Church of Satan, he decided that the symbol was the one which most fully embodied the principles which were the bedrock of the Satanic church. Contrary to claims made against the Church by detractors, LaVey never claimed to have created this particular symbol.[7] In its formative years, this particular version of the symbol was utilized by the Church on membership cards, stationary, medallions and most notably above the altar in the ritual chamber of the Black House.
 
 
Source: Wikipedia