🔼The history of the name Mezuzah
A Mezuzah is one of two phylacteries that are prominent in Jewish liturgy (the other being Tefillin). The Mezuzah is a small container that people attach to their door posts, according to strict rules that have evolved over the centuries. It contains a piece of parchment with written on it the words of Deuteronomy 6:4-9.
The Tefillin originates from a literal application of Exodus 13:9, and the Mezuzah originates from a reading of Deuteronomy 6:9 and 11:20. These latter two texts appear to refer to the entire Law of God, but Jesus sums this up by quoting Deuteronomy 6:5 and Leviticus 19:18 (Matthew 22:37-40). The chances are excellent that Jesus didn't invent this summary, but that this understanding was already widespread in Judea. The love-your-neighbor part didn't make it into the traditional Mezuzah, but the love-the-Lord bit certainly did.
The Oxford Companion To The Bible states that "according to rabbinic tradition, both [phylacteries] could be written from memory. Hence it is not surprising that many of the texts found from Qumran and the Judean wilderness caves contain departures from the Masoretic Text. In addition, there is great variation in the passages selected from the Bible that were inserted into the compartments".
The Oxford History Of The Biblical World adds to this: "The individual manuscripts of the Hebrew scriptures, as well as the Tefillin and the Mezuzot, sometimes match the Hebrew versions now standardized in synagogue worship. Sometimes they conform to the version familiar from the Septuagint [...]. Sometimes they differ from both".
It's not clear when people actually started attaching Mezuzot to their doorposts, or when the name Mezuzah came into practice. The Random House Dictionary cheerfully states that the common word mezuzah became applied to this doorpost-attached phylactery sometime around 1640-1650, but Erika Meitner writes in American Sanctuary — Understanding Sacred Spaces: "By the Second Temple Period (first century BCE), the word [Mezuzah] had been applied to the scroll Jews hung on their doorframes..".
The historian Josephus (1st century AD) commented on the Mezuzah in his work Antiquities of the Jews, saying, "The greatest benefits of God are to be written on the doors . . . in order that His benevolent providence may be made known everywhere" ("Ant". iv. 8, 13).
In the twelfth century AD, the great sage Maimonides wrote, "By the commandment of the Mezuzah man is reminded, when coming or going, of the unity of God, and is aroused to the love of Him. He is awakened from his slumber and his vain worldly thoughts to the knowledge that nothing endures in eternity like the knowledge of the Rock of the World. This contemplation brings him back to himself and leads him on the right path" (Yad, Tefillin, vi. 13).
🔼Etymology of the name Mezuzah
The name Mezuzah is the same as the noun מזוזה (mezuza), meaning door- or gate-post. It comes from the root זוז (zwz I), which probably meant to move or to rise:
The name Mezuzah literally means Doorpost, but is nowadays readily applied to the phylactery.