According to one of the mañaina in this family, the Kådi' are descendants of Jose Cepeda Manibusan (born around 1857) and his wife Maria Pangelinan. Apparently they had a lot of children, the majority of them boys, so the Manibusan name enjoyed much security of staying around.
But what does the nickname mean? According to the story told by the mañaina, Jose liked to go the extra yard when entertaining guests. Serving guests more fancy food and so on. According to the story, "kådi'" means to show off, to be "ande'." But a search of that word in the dictionaries turns up nothing. So, it remains a puzzle.