O King of nations, and their Desired, the Cornerstone Who dost make both one: come and save mankind whom Thou didst form out of clay.In the Authorised Version, Haggai 2:6-7
For thus saith the LORD of hosts; Yet once, it is a little while, and I will shake the heavens, and the earth, and the sea, and the dry land; and I will shake all nations, and the desire of all nations shall come: and I will fill this house with glory, saith the LORD of hosts.
It is tempting to read this as the source for the exspectatio gentium of the O Emmanuel or the desideratum gentium of O Rex. Indeed the Vulgate (v. 8) reads et veniet desideratus cunctis gentibus
The Septuagint reads καὶ ἥξει τὰ ἐκλεκτὰ πάντων τῶν ἐθνῶν - transliterated (caps for long vowels) kai hExei ta eklekta pantOn tOn ethnOn - the choice things of all the nations.
The literal interlinear translation of the Old Testament edited by John R Kohlenberger III has: and they will come one desired of all of the nations. That suggests that thesauri (treasures) is correct and not desideratus (desire).
[Please don't ask me to untangle the differences between the Neo-Vulgate and its predecessors - is it simply a better edition of Jerome's single text, did Jerome produce many translations and this is another selection than the received text? is it merely an improved translation from the Hebrew?]