I do not think this symbol is nor used (in addition with a letter), nor ever called anything but "backtick". it's not an "accent grave" (even if it might be used as it), but a revert appstrophe - backtick or backquote.
With a Danish Mac layout, to type ` I press it then press space. To type è, ì etc, I press `, then press the vowel. Similarly I can use the keys marked ¨ ^ and ´. (The Danish letters æ, ø, å have their own keys, since they are used very frequently.)
So, I would never call it "backtick", since it is a grave accent.
ASCII-1967 isn't online but EMCA-6-1973 is functionally equivalent. https://www.ecma-international.org/publications/standards/Ec...