I just saw on Imabi.net :
http://www.imabi.net/karanodenoda.htm
That 「ので」 is actually the て form of the explanatory particle の with だ...
It actually makes a lot of sense if it is true. I`ve always been taught that 「ので」, 「から」 and 「の(だ/です)」 are 3 different things and I used them without actually knowing where they come from.
So if it is true :
明日は学校に行かない。風邪を引いたんだ。: Tomorrow I`m not going to school. Because I got a cold.
風邪を引いたんで、明日は学校に行かない。: Because I got a cold, tomorrow I`m not going to school.
Are those two sentences exactly the same and there is no difference in meaning between the 「んだ」 and 「んで」 ?
Thanks a lot!
Edit :
On the dictionary, it is written that 「ので」 comes from the particule の + the 格助詞 で. So if it is the て form of のだ, then the 連用形 of だ is the 格助詞 で?