The Hertz Chumash The Pentateuch and Haftorahs has an excellent, concise, and thorough discussion of the term translated 'Shiloh' in the King James Version on pages 201 and 202. He characterizes the JPS translation of עַד כִּי-יָבֹא שִׁילֹה ('as long as men come to Shiloh') as an unsatisfactory translation. In his brief discussion on page 185, he favors the Septuagint translation, where the clause is rendered as 'until that which is his shall come.' As he reads it, this means that 'Judah's rule shall continue till he comes to his own, and the obedience of all the tribes is his.' Alternatively, 'it may also mean that when the tribe of Judah has come into its own, the sceptre shall be taken out of its hands.' While acknowledging that שִׁילֹה was understood as a name of the Messiah in Rabbinic literature, he indicated on page 202 that this interpretation was homiletic and non-binding (it occurs in the Gemara, not the Mishnah). The King James Version's 'till Shiloh come' is wrong.
The NJPS also does not render the Hebrew word as 'Shiloh' but as 'tribute to him,' as in the Midrash, where it is understood to be a contraction of shai loh: 'so that tribute shall come to him'. In a footnote, however, it admits: 'Meaning of Heb. uncertain.'
See further Jonathan Kolatch and Berel Wein, Masters of the Word: Traditional Jewish Commentary From the Eleventh Through Thirteenth Centuries (Ktav, 2006), pp. 267-389 for an even more in-depth discussion than that of Rabbi Hertz. Much of it can be accessed online at Google Books.com and is highly recommended.
 So Babylonian Talmud Sanhedrin 98b. This is where the earliest occurrence of Shiloh as a name for the Messiah is found. The German Bible of Sebastian Münster in 1534 was the first version to use it, and it became current in Protestant versions and commentaries after that.
 His argument there that Shiloh does not occur anywhere in Scripture as a name of the Messiah overlooks the fact that it does so occur in this very verse in the Leeser Bible (1853), both in the translation ('until Shiloh come') and twice in the unusually extensive footnote ('The assumption that the sceptre was taken at a particular period, wherefore Shiloh must have come then, is futile,' 'The sceptre will return when the Shiloh, the King Messiah, shall come'). He cites Targum Onkelos and Rashi as support for his interpretation that שִׁילֹה refers to the Messiah, but neither read שִׁילֹה as a personal name though the passage was regarded as referring to the Messiah and his kingdom. The Leeser Bible can be found online at Internet Archive.com.