The nut does have a name, 359613-S2, and it is used on the body to attach the lower rear part of the front fender to the body (ref "1967 Mustang Body Assembly Manual", AM0016 pg 9 item L).
Jim
"A Name"? Maybe or maybe better referred an 'identification number" IMHO
Wouldn't want to be referred to, myself, by my Social Security Number though many places use that as an identification
Just like many things - different terms for same or similar things. Just as long as we establish that were "talking" about the same thing
But thanks for providing the identification number of the part so others can make use of it if there is a need