A divagation must be made, to bring the reader to a comprehension of the custom surrounding mattu, a word signifying change, i.e., change of cloth, which is of sufficient importance to demand explanation. When a man or woman is outcasted, the washerwoman (or man) and the barber of the community (and no other is available) are prohibited from performing their important parts in the ceremonies connected with birth, death, and menstruation. A person who is in a condition of impurity is under the same conditions; he or she is temporarily outcasted. This applies to Nambutiris and Nayars, as well as to the Tiyans. Now the washerwoman is invariably of the Tiyan caste. There are Mannans, whose hereditary occupation is washing clothes for Nambutiris and Nayars, but, for the most part, the washerwoman who washes for the Nayar lady is of the Tiyan caste. A woman is under pollution after giving birth to a child, after the death of a member of her tarvad, and during menstruation. And the pollution must be removed at the end of the prescribed period, or she remains an outcaste--a very serious thing for her. The impurity is removed by receiving a clean cloth from the washerwoman, and giving in exchange her own cloth to be washed. This is mattu, and, be it noted, the cloth which gives mattu is one belonging to the washerwoman, not to the person to be purified. The washerwoman gives her own cloth to effect the purification. Theoretically, the Tiyan has the power to give or withhold mattu, and thus keep any one out of caste in a state of impurity; but it is a privilege which is seldom if ever exercised. Yet it is one which he admittedly holds, and is thus in a position to exercise considerable control over the Nambutiri and Nayar communities. It is odd that it is not a soiled cloth washed and returned to the person which gives purification, but one of the washerwoman's own cloths. So the mattu may have a deeper meaning than lies in mere change of cloth, dressing in a clean one, and giving the soiled one to a person of inferior caste to wash. This mattu is second in importance to no custom. It must be done on the last day of pollution after birth and death ceremonies, and menstruation, or the person concerned remains outcasted. It is noteworthy that the Izhuvans know nothing of mattu.