E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A charm or amulet. The Jews wore on their wrist or forehead a slip of parchment bearing a text of Scripture. Strictly speaking, a phylactery consisted of four pieces of parchment, enclosed in two black leather cases, and fastened to the forehead or wrist of the left hand. One case contained Ex. xiii. 110, 1116; and the other case, Deut. vi. 49, xi. 1321. The idea arose from the command of Moses, Therefore shall ye lay up these my words in your heart and bind them for a sign upon your hand as frontlets between your eyes (Deut. xi. 18). (Greek, phylactrion, from the verb phylasso to watch.)