On the incongruous presence of 7 in “September”

— I saw a weird looking sign, my husband tells me, on a Chinese restaurant. It had a large “七” – Chinese for 7 – with, underneath, the mention “Sept”.
— Yeah, “sept” is French for “seven”.
— What! (He reacts as if I’ve just proffered the most absurd of facts.) But isn’t sept the abbreviation of [...]