kaddish
n.
5Aram kadish, lit., holy, akin to Heb kadosh, holy root kdt, sanctify6 Judaism a hymn in praise of God, recited as part of the daily service or, in one form, a mourner‘s prayer

From the Internet:
"The final period of formal mourning is avelut, which is observed only for a parent.
This period lasts for twelve months after the burial. During that time, mourners avoid
parties, celebrations, theater and concerts. For eleven months of that period,
starting at the time of burial, the son of the deceased recites the mourner's Kaddish
every day. "