Rebbi Yehoshua ben Levi said: Tzemach is his name. Rebbi Yudan son of Rebbi Aibu said: Menachem is his name. Said Chanina son of Rebbi Abahu: They do not argue, for the numerical value of each is the same – he is Tzemach; he is Menachem. * From Chapter Fifteen of Rabbi Shloma Majeski’s Likkutei Mekoros, Volume 2. (Underlined text is the compiler’s emphasis.)
The Rabbis said: Who is Moshiach the King? If he is among the living, his name is Dovid, and if he is among those already deceased, then he is Dovid. (If he is among the living: If he is among the living, his name will be Dovid, and if he is among the deceased, it will be Dovid himself. ––P’nei Moshe)
Rebbi Tanchuma said: The reason [why Moshiach’s name must be Dovid is as it is said] “And He does kindness to His anointed, to Dovid.” (To His anointed, to Dovid: Dovid is eternally His anointed. ––P’nei Moshe)
Rebbi Yehoshua ben Levi said: Tzemach is his name. Rebbi Yudan son of Rebbi Aibu said: Menachem is his name. Said Chanina son of Rebbi Abahu: They do not argue, for the numerical value of each is the same – he is Tzemach; he is Menachem. (He is Tzemach; he is Menachem: They are both equal according to Gematria. ––P’nei Moshe)
(Talmud Yerushalmi, Brachos 17)