Citing someone directly with additional information in footnote

I would like to directly quote some sentences of another author who uses a word A which is a synonym for a word B I'm using in my text. Note: I would like to use my word B as the word A is very rare.

So I placed the text of the author into quotation marks and a footnote at the word A stating that in the following the word B will be used in my text. At the end of the quotation I put the source of the quote.

Is that correct or could it be misinterpreted as a footnote of the text I'm quoting? Should I add e.g. "Authors note:" before my footnote text?