I think this may be a very common question(but not for me). Can someone please tell me how did the text of Kaddish first compiled?
This summary brings up the following on page 6
Concerning the origin of Kaddish that you asked, we can not trace the practice to a clear and definitive source found among our ancestors’ writings. However, those who followed them based their recitation of Kaddish upon this verse (Leviticus 22, 32) And I will be sanctified within the people of Israel and upon what our Rabbinic leaders extrapulated from the verse: that any prayer which results in the sanctification of the name of G-d must be recited only in a group of ten men.
From theses teachings we can conclude that when ten men congregate to perform a mitzvah, whether it be for prayer or for the study of Torah, they must recite a prayer in which they sanctify the name of G-d. As a result, at the conclusion of the first section of the morning prayer, Pseukei D’Zimra, after reciting the Bracha in Yishtabach, those congregated should recite Kaddish because they have the completed the mitzvah of reciting Pseukei D’Zimra and they are about to perform an additional Mitzvah, the recital of Kriyat Shma and its blessings before and after . . .
And they should recite Kaddish after Shmona Esrei because it too is an independent Mitzvah and it is not connected with that which is recited after it. And another Kaddish should be recited after the Torah Reading because in order to read from the Torah, ten men must congregate together. And another Kaddish after reciting the Kedusha in OO”Vah L’Tzion because it too is a Mitzvah unto itself and it is a Prayer of Sanctification of G-d’s name and requires the presence of ten men.