The Greek geographer Pausanias also recorded the use of a magickal book in his second century Guide to Greece. He referred to a magickian making dry wood catch fire after he, “in his native language had sung hymns, and pronounced certain barbarous words, out of a book which he held in his hand.”
The origin of the name ‘Book of Shadows’ seems to be contemporary with Gardner’s novel High Magic’s Aid. A copy of the magazine The Occult Observer from 1949 contained the term ’Book of Shadows’ in an article by the palmist Mir Bashir about an ancient Sanskrit divination manual of the same name. Significantly, The Occult Observer was published by Michael Houghton, the then proprietor of the Atlantis Bookshop in Bloomsbury, London, which also published High Magic’s Aid by Gerald Gardner in the same year under its publishing imprint of Neptune Press.
Earlier uses of the phrase do occur, though the only esoteric occurrences are in Christian works which are clearly unrelated to the Wiccan tradition, such as this reference from a few years earlier in 1942:
“According to Charles Wesley, the Old Testament is a book of shadows, of which Jesus is the substance.”
 The Evangelical Doctrines of Charles Wesley’s Hymns, Rattenbury, 1942
<1> The Religion of Babylonia & Assyria, Jastrow, 1893, also quoted in The Book of Witches, Hueffer, 1908
<2> An Historical Essay Concerning Witchcraft: With Observations Upon Matters of Fact, Hutchinson, 1718
Extract from: Wicca: Magical Beginnings written by d’Este & Rankine, 2008 (Avalonia.) PB / Kindle @ https://amzn.to/3Ay4HJr. Shared here with the intention to inspire and inform the now and future generations interested in Wicca and other Pagan traditions inspired by it.