The Kaddish prayer was not originally associated with mourning at all. It was used in the house of learning, Beth Midrash, to conclude a session with the Rabbi. The Kaddish Derabbanan, i.e. the Rabbis’ Kaddish, is probably the earliest prayer. Its purpose was to express the hope in the messianic era when the name of God would be magnified and sanctified in the world.
The Kaddish came into the synagogue from the house of learning. Its Hebrew title was never the Mourner’s Kaddish.
It has several titles depending in which part of the service it is recited. It is recited both at the conclusion of a main service, i.e. Shacharit or Musaph, immediately after the Amidah; or to indicate the end of an important section in the service. The Kaddish, which is recited by a mourner, is called Kaddish Yatom, the Orphan’s Kaddish. It is recited after Aleinu Leshabe’ach and some Psalms, which are recited, mostly, at the end of the service.
In mystical circles the belief spread, in the middle ages, that if a son recites Kaddish, publicly, in honour of his parent, it has the power to rescue him from the judgment, which takes place in the heavenly court, in the first year after their death. It is believed that the son’s Kaddish gives contentment to the soul as it gradually migrates into the heavenly worlds and joins the divine shelter, where the souls reside.
According to this mystical tradition, Kaddish is reserved exclusively to sons. It is associated with their commitment to come to shul regularly and to uphold the communal Minyan. It is, therefore, not customary to encourage women to recite Kaddish for their parents.
Kaddish is not, traditionally, a prayer which we say together as a congregation. On the contrary, only one person should be reciting it in the presence of the congregation which listens to it very carefully and responds with concentration and passion. The most important response in the Kaddish is YEHE SH’MEI RABBA MEVORACH LA’ALAM ULEOLMEI OLMAYA. According to Jewish law, it should be said very loudly and clearly. In Yeshivot, particularly, where hundreds of students participate in the service, this response makes a great impact. This response is as important as the recitation of the Kaddish itself.