During Mozart's illness, a stranger visited him. This man (who kept his appearance concealed) wanted him to compose a mass for the dead. He was obsessed at this point that he was writing his own Requiem and so although he was ill, he completed parts of it and a basic outline, of which he discussed with his understudy Franz Sussmayr. He "made Sussmayr familiar with his further plans for the work, showed him the outlines of the unfinished movements and explained how they should be completed."�(1) Seven weeks after his death it was finally finished. It was then discovered that the man who came to Mozart was Count Franz Von Walsegg. He wanted a requiem written for his wife's funeral. He also desired to pass it off as his own, which is why he kept hidden from Mozart. Because nobody defended Mozart right away, the Count was able to take credit for it and rename it as his own. It wasn't until 1799 when it was first published that Constanze revealed the truth that Mozart did not finish it and that it was not written or completed by the Count.
I f we take a look at the Kyrie (in the beginning) and the Cum Sanctis Tuis (the last part) you will notice that the form, and notation are exactly the same. Before Mozart passed away, he fully orchestrated and completed this part of the mass. Susssmayr, who was given the task to "fill in the unfinished parts"�, decided to repeat the Kyrie part with different text. Because this part of the mass is the communion and confirmation part, Sussmayr felt that there would be a connection with the beginning, the confirmation and forgiving part.
Kyrie eleison, Christe eleison, Kyrie eleison translates to Lord have mercy upon us, Christ have mercy upon us, Lord