Phylactery - Vine's Expository Dictionary of New Testament Words
Phylactery[ 1,,G5440, phulakterion ]
primarily an outpost," or "fortification" (phulax, "a guard"), then, "any kind of safeguard," became used especially to denote "an amulet." In the NT it denotes a prayer fillet, "a phylactery," a small strip of parchment, with portions of the Law written on it; it was fastened by a leather strap either to the forehead or to the left arm over against the heart, to remind the wearer of the duty of keeping the commandments of God in the head and in the heart; cp. Exodus 13:16; Deuteronomy 6:8; Deuteronomy 11:18. It was supposed to have potency as a charm against evils and demons. The Pharisees broadened their "phylacteries" to render conspicuous their superior eagerness to be mindful of God's Law, Matthew 23:5.