Why did the people believe that no one would know where the Christ came from? In John 7:25-27, Jesus is speaking to a crowd of people.  They seem pretty impressed with Him and begin to wonder if He could be the Messiah.  However, one of their objections is that they know where He came from.  They believe that when the Christ comes that no one will know where He came from.


  Some of the people of Jerusalem therefore said, “Is not this the man
  whom they seek to kill? 26 And here he is, speaking openly, and they
  say nothing to him! Can it be that the authorities really know that
  this is the Christ? 27 But we know where this man comes from, and when
  the Christ appears, no one will know where he comes from.”  John
  7:25-27 ESV


Where, then, did they get the idea that no one would know where the Christ came from?
In John 7:27, it is written,

Rather, we know where this man is from, but when the Messiah comes, no one knows where he is from.
ἀλλὰ τοῦτον οἴδαμεν πόθεν ἐστίν ὁ δὲ Χριστὸς ὅταν ἔρχηται οὐδεὶς γινώσκει πόθεν ἐστίν

According to the Gospels, &quot;the chief priests and the scribes&quot; understood that the Messiah was to be of the seed of David and born in Beit-Lechem (Matt. 2:4-5; John 7:42 cp. Mic. 5:2).
People were cognizant of Yeshua's parents (Mark 6:3; John 1:45 cp. John 6:42) and the town he resided in, Natzaret of Galil (Matt. 21:11; John 7:41).
On the other hand, it was prophesied that the Messiah would be born of a virgin (Isa. 7:14 cp. Matt. 1:23) and be the seed of a woman (Gen. 3:15). Essentially, a human male would not contribute to the conception of the Messiah.
"Seed from another place"
In the Midrash Bereshit Rabba, Parashat Bereshit, it is written,

&quot;…and she called his name Set, for God appointed me another seed…&quot;
(Gen. 4:25). Rabbi Tanchuma in the name of Rabbi Shemu'el said, &quot;She
observed the seed that came from another place. And what is this?
This is the King Messiah.&quot;
ותקרא את שמו שת כי שת לי אלהים זרע אחר וגו׳ רבי תנחומא בשם רבי שמואל
אמר נסתכלה אותו זרע בא ממקום אחר ואי זה זה מלך המשיח

The midrash states that the seed from which the Messiah would be conceived would come &quot;from another place&quot; — perhaps an allusion to him being of divine origin.
"Root from dry ground"
Another scripture which seems to hint at a peculiar childhood of the Messiah is Isaiah 53:2.
In his Epistle to Yemen (Iggeret Teiman), Rabbi Moshe ben Maimon (Rambam) wrote,

And, Yesha'yahu (Isaiah) said similarly, when he (the Messiah) appears
without knowing his father and mother and family: &quot;And he will grow up
in His presence as a branch, even like a root out of dry ground (etc.)...&quot;
(Isa. 53:2).
וְאָמַר יְשַׁעְיָה כְּמוֹ כֵן, כְּשֶׁיִּרְאֶה מִבְּלִי שֶיודע לוֹ אָב
וְאֵם וּמִשְׁפָּחָה, &quot;וַיַּעַל כַּיּוֹנֵק לְפָנָיו וְכַשֹּׁרֶשׁ&quot;
וְגוֹמֵר יְשַׁעְיָה נ&quot;ג ב'.

Rambam wrote that the Messiah would not know his father, mother, or family. While this isn't true of Yeshua, it demonstrates a traditional Jewish interpretation concerning the Messiah which Rambam received. It is quite possible that this same tradition existed among the Jewish people in the time of Yeshua. That is, some believed that the Messiah's father, mother, and family would be unknown and that the Messiah would appear from obscurity.
Perhaps one of the reasons Rambam interprets the scripture in such a manner is because the ground is said to be &quot;dry.&quot; A root in dry ground is essentially dead or on the verge of death, as it receives no sustenance. Trees and plants are often used as metaphors in reference to ancestors. For example, the Messiah is said to be the &quot;root of Yishai&quot; (Isa. 53:11). That the Messiah, the root of Yishai, grows up out of dry ground, indicates that he is from an obscure family, contrary to the belief that the Messiah would be a well-known public figure worthy of pomp and grandeur.
I have also read that Raymundi Martini, in his Pugio Fidei, quotes Rabbi Moshe Ha-Darshan in saying that the Messiah would be fatherless, by connecting Zech 6:12 to Isa. 53:2 and Ps. 110:3 (according to the thought of the LXX). I'm currently searching the Pugio Fidei attempting to locate the page.