The expression "shabbat shalom," literally, "Sabbath of peace," is neither modern nor secular in origin. … [I]t originated in the Galilee, in the city of Safed, in the mystical circle of renowned kabbalist Isaac Luria (1534-1582) — also known by an acronym of his name, forming the Hebrew word for "The Lion," as Ha-Ari.
Luria and his disciples had many unique practices, the best guide to which can be found in the Hebrew book "Hemdat Yamim," "The Adornment of Days," written in Jerusalem in the 17th century. Although its anonymous author was not, as he was once reputed to be, Nathan of Gaza, the "prophet" and apostle of the false Messiah Sabbetai Zevi — he apparently was, besides being a follower of Lurianic customs, a Sabbatian sympathizer. In a chapter on Sabbath observance, he declares that after leaving synagogue at the end of the Musaf service Saturday morning, a Jew should "go directly home in great joy instead of meandering here and there [to visit friends or neighbors] and say in a loud voice when he enters [his home], 'Shabbat shalom u'mevorakh,' and sit down at the table dressed in white like an angel of God."
The word u'mevorakh, which means "and blessed" in Hebrew, is puzzling in this context, inasmuch as, a grammatically masculine and singular form , it is not clear to whom or what it refers. It cannot be to the Sabbath, since shabbat in Hebrew is feminine, as is the traditional image of the Sabbath as a queen or bride; yet neither can it be to the members of the greeter's family, in which case it would be u'mevorakhim, in the plural. Perhaps it refers to the good angel who, in kabbalistic belief, accompanies every Jew during the Sabbath and is here being welcomed to the greeter's home, just as the Sabbath angels are welcomed in the hymn Shalom aleykhem, mal'akhei ha-sharet ("Welcome in peace, ministering angels"), that is traditionally sung around the Friday night table. Perhaps the answer lies in some other Lurianic precept.
 Hemdat Yamim was very popular among the early leaders of the Hasidic movement.
 If the custom was of Sabbatian origin, 'u'mevorakh" does make sense. It would be referring to Shabbatai Tsvi, who was thought to be in a "mystical union" with both the shekhina and the "Shabbat Queen."
 Can anyone trace "Shabbat Shalom" to before Shabbatai Tsvi? If not, why not?