These two songs by Ravel were written in 1914 at Saint-Jean-de-Luz. The first song Kaddisch uses an Aramaic text from the Jewish prayer book; L'Énigme éternelle is based on a traditional Yiddish verse. They were first performed in June 1914 by Alvina Alvi (who commissioned them) with Ravel at the piano. Ravel orchestrated the songs in 1919-1920.
The text of L'Énigme éternelle can be found on the Lied and Art Song Texts Page.
Ravel had earlier made one other setting of a Hebrew song with the Chanson hébraique, which formed one of the Chants populaires.
[On the subject of the the text and liturgical function of the traditional Kaddish, Boaz Tarsi has written the following:
"Written in a mixture of Hebrew and Aramaic the Kaddish is about a half-page long text, primarily magnifying and glorifying God, as well as expressing a wish for a speedy coming of the Messianic era. It is recited primarily in the synagogue service after principal sections of the liturgy or at the beginning of such sections. There are four main types of the synagogue Kaddish [there is also a fifth type recited at the cemetery], each containing a slightly different version of the text. In most occasions the service leader sings the Kaddish, with some congregational responses. The two main exceptions are the Kaddish recited by people in mourning or observing a death's anniversary (Kaddish Yatom), and the Kaddish recited after a study session (Kaddish Derabannan). On these occasions the Kaddish is normally not sung but rather spoken out loud by the mourners or those who finished a study session." ( Boaz Tarsi, "Observations on Practices of Nusach in America," Asian music, Volume xxxiii-2, 2002).
Dr Tarsi also gives the following approximate translation of the text of the Kaddish set by Ravel:
Magnified and sanctified be the name of God throughout the world which He has created according to His will. May He establish His kingdom during the days of our life and the life of all speedily and soon and let us say Amen. (Here normally comes a congregational response, which is missing from Ravel's setting). Exalted and glorified, lauded and praised, acclaimed and honored be the name of the Holy One blessed be He, praised beyond all blessings and hymns, beyond all tributes that mortals can express and let us say Amen.]