ET CETERA, as we know, is a Latin expression. From ETC, we read:
Et cetera, usually abbreviated etc., comes from the Latin et, meaning and, and cetera, meaning the rest.So et cetera literally means and the rest.
So, it is indeed a Latin expression. And what does that mean? Obviously that we DO NOT have to respect its original meaning.
For instance, see quorum on Latin: The original meaning was of whom, but we now use it to point at minimum number of members.
Because the expression comes from a different language, we can actually do pretty much whatever we like, so that the sense of the expression is a bit lose. In this case, we could easily be accepting both and etc. and etc.
I used to write etc., just because that matches the Brazilian usage of the expression, but I then found a website where a lady who said that she was an expert advised us t0 always write and etc. instead. I then started putting it like this everywhere. Later on, I thought of the meaning in Latin, for et can only be and, and I then thought that we should write in the way I used to, that is, in the way Brazilians do, that is, etc. only.
I am now inclined to think that we can easily include both writings in our collection of whatever is advisable and be then allowed to write both and etc. and etc. I think that language should never complicate communication and, if possible, it should simplify it.