From T.P. Meenakshisundaran's A History of Tamil Language, from a chapter that talks about loan words from Portuguese-
"...tocai is from doce which was the name of a sweet dish; by the process of semantic extension, this has come to mean any rice cake."
Who'd have thunk it?
So what was the dosai (or tocai, which is how I pronounce is anyway) called before the Portuguese arrived in Tamil land? Surely, dosais predate Portuguese colonisation? According to this article, dosais have a two thousand year history in TN.
Why then, has the dosa/dose usage been adopted in the other southern states? Unless dosai-making spread out of TN only in the last three-four hundred years or so. Does anyone even know that dosais were invented in TN? I remember reading somewhere that they are an Udupi creation. Hmm...
Meenakshisundaran also insists that the Tamil vattu comes from the Portuguese word for duck (which quick googling reveals to be pato). Come to think of it, I can't seem to recall a single reference to ducks from what little classical/Bhakti era Tamil poetry I know. By way of aquatic birds, swans and cranes, yes. But ducks, no. Interesting, but why/how? Anyone know the Malayalam/Telugu/Kannada word for duck?
But said article claims that fermentation techniques were brought to South India from Indonesia sometime during the years, 800-1200 AD. Hello? No fermentaion, no dosai.