The Athame is a black-handled, double-edged knife, and its name is the more debated word in the whole Wiccan toolkit. No printed grimoire before the twentieth century uses it: Ronald Hutton traces the term through a chain of manuscript copying, from continental grimoire words for a black-handled knife (arthane, arthana and related forms recorded in versions of the Key of Solomon and its descendants) mangled across successive scribal transmissions until Gerald Gardner's circle fixed the spelling in the mid twentieth century Book of Shadows.
The underlying tool is older than the word. Grimoires such as the Key of Solomon and the Grand Grimoire specify a black-handled knife among the magician's instruments centuries before Wicca existed, used to trace and to command rather than to cut, and Owen Davies's history of grimoire literature places this instrument within a wider furniture of consecrated tools, wands, swords and knives, that ceremonial magic handed down through print and manuscript across four centuries. Gardner drew on this older stock along with material from the Hermetic Order of the Golden Dawn and Aleister Crowley's Thelemic ritual, assembling a working toolkit that reads, tool by tool, as a synthesis of several older traditions rather than an invention from nothing. The double edge, the black handle and the drawn sigils some lineages inscribe on the blade all have grimoire-era precedent, even where the specific word Athame does not.
Sources The Triumph of the Moon: A History of Modern Pagan WitchcraftRonald Hutton with Grimoires: A History of Magic BooksOwen Davies