Amusingly, people were asking this question in 2000.   I found this in comp.unix.shell:

in news: at.linux, there's a discussion about why the
interpretersymbol #! is called shebang (you can imagine, which
theories already occurred). but does anybody know, WHY this is really
called shebang?

sorry for being a bit offtopic, but it's essential :)

thanks before.

Stefan

No origins were found in the messages other than a guess that it was a cute shortening of “SHARP BANG.”

Wasn’t it Ken Thompson who said if he had it to do over again he’d have put an “e” on the end of create.    Five decades of calling it “CREE – AT”