Unix didn't use to support '#!', a brief history

Octothope was coined by Bell Labs. It is certainly not jocular (what?). In point of fact, it is that symbol's proper name and how it is referred to in all Bell manuals and documentation, and this word coinage is little to no different to how the British began using # for pound to distinguish it from £, the currency.

Even though "hash," by hundreds of years, predates all other names for the symbol (originally, "hatch," marks one would make with a hatchet), hashing, the mathematical practice since the 1940's of transformation of a string of characters into a usually shorter fixed-length value or key that represents the original string, was not married in identity or meaning or abbreviation to the # symbol by convention until probably 1990, regardless of location on the planet or country not in North America. No one anywhere in the universe was using the hash symbol in, say, 1975, to refer to the mathematical hashing in computer science. In 1975, the # was the octothrope properly and most commonly (even if no one used that term, they all had a telephone and they still do, and every telephone today still has an octothorpe button, i.e. not a hash button), or the number sign or the pound sign by popularity.

# was never used as an abbreviation for mathematical hashing, again, until maybe late 1980's, probably like about 1991 # became conventionally used by programmers, computer scientists and mathematicians to mean mathematical hash. And even today, every county in the world that has telephones properly has an octothorpe key, not a hash or pound key. Bell coined the term and established it's usage long, long before # was used for math hashes, and even to this day, the octothorpe symbol is likely more common than the hash symbol, just because there are so many damn phones.

> Perhaps an alteration of shebeen (q.v.), but shebang in the sense "tavern," a seemingly necessary transitional sense, is not attested before 1878 and shebeen seems to have been not much used in the U.S. Bartlett's 1877 edition describes it as "A strange word that had its origin during the late civil war. It is applied alike to a room, a shop, or a hut, a tent, a cabin; an engine house."

> Phrase the whole shebang first recorded 1869, but relation to the earlier use of the word is obscure. Either or both senses also might be mangled pronunciations of French char-à-banc, a bus-like wagon with many seats.

https://www.etymonline.com/word/shebang