Fady is not strictly a taboo, it is more a belief which signals when something is "dangerous" related to action, food, locations etc. The Malagasy word fady (pronounced fahdy) is of Indonesian origin.
Abstinence, fasting, prohibition; unlawfulness, incest; anything tabooed. It often takes an accusative case, as: fady ahy izany. Faly is used in the provinces. -- Rev. James Richardson (1844-1922)
"The most comprehensive translation of fady is "prohibition" or "prohibited", referring to what one is not allowed to do, objects with which one must not come into contact, words which must not be uttered, places which must be avoided. They become fady-actions, fady-objects, fady-words, fady-places respectively. These are all negative expressions: thou shalt not. At the same time the taboos point to the objects, actions and persons concerned, and put a distinct mark on them. Fady is a sign of warning, indicating that it is very dangerous to have anything to do with what is prohibited. The transgressor becomes on the one hand taboo to himself, regarding the matter as personally felt, and on the other hand he becomes taboo to his environments and his fellows.
That which is taboo, however, is not dangerous as long as there is no profanation. A sacrificial place is simply a place where sacrifices are offered, and need only be dreaded if it is defiled by untimely actions or unseemly behaviour, in other words, if the sacred place is looked upon in a non-ritual way. It can only be approached ritually. A corpse is simply looked upon a corpse, a dead human being, and a number of different reactions and feelings are linked to it. It is only by coming into contact with the corpse that one gets unclean. Thus fady is always connected with particular actions and situations where transgression is possible." -- Jorgen Rudd (1901 - 1968), missionary