Phylactery

[fi-lak-tuh-ree] /fɪˈlæk tə ri/

noun, plural phylacteries.
1.
Judaism. either of two small, black, leather cubes containing a piece of parchment inscribed with verses 4–9 of Deut. 6, 13–21 of Deut. 11, and 1–16 of Ex. 13: one is attached with straps to the left arm and the other to the forehead during weekday morning prayers by Orthodox and Conservative Jewish men.
2.
(in the early Christian church) a receptacle containing a holy relic.
3.
an amulet, charm, or safeguard against harm or danger.
/fɪˈlæktərɪ/
noun (pl) -teries
1.
(Judaism) (usually pl) Also called Tefillah. either of the pair of blackened square cases containing parchments inscribed with biblical passages, bound by leather thongs to the head and left arm, and worn by Jewish men during weekday morning prayers
2.
a reminder or aid to remembering
3.
(archaic) an amulet or charm
n.

late 14c., “small leathern box containing four Old Testament texts,” from Old French filatiere (12c.) and directly from Medieval Latin philaterium, from Late Latin phylacterium “reliquary,” from Greek phylacterion “safeguard, amulet,” noun use of neuter of adjective phylakterios “serving as a protection,” from phylakter “watcher, guard,” from phylassein “to guard or ward off,” from phylax (genitive phylakos) “guard,” of unknown origin. Sometimes worn on the forehead, based on a literal reading of scripture:

Ye shall bind them [my words] for a sign upon your hands, and they shall be for frontlets between your eyes. [Deut. xi:18]