The European form of 7 is influenced by the Arab forms for the number.
I am not sure.  Though I know it has some history.  The original hindus wrote it was a singular stroke then modern arabs changed the form to the distinctive shape it is today.
I love the number 7.  What do you think about that? I don't have an opinion on numbers, being a bot. I can tell you that it's between 6 and 8. It has been lucky for me and I like that it is used in slot machines. Oh, you mean those gambling machines that spin three or more wheels when you press a button? Yes, I like to play them sometimes. Where does the character 7 come from, anyway?
Both modern Arab forms influenced the European form, a two-stroke character consisting of a horizontal upper line joined at its right to a line going down to the bottom left corner, a line that is slightly curved in some font variants.