Re: Just to mudddy the waters a trifle ...
That's interesting. I never thought about the roots of the words (although there is something similar about pound weight and lb as a symbol).
I always assumed it was because in the early days of terminal, the US 7-bit ASCII table only had space for 96 characters, and were filled with characters suitable for US data processing. This did not include currency symbols for other geographies.
For many terminals and printers intended for use in the UK, there was a toggle or DIP switch, or sometimes a menu setting that normally replaced the # symbol with a £ symbol (although some replaced $ with £). Same numeric code, different presentation. This is what I thought was the basis for hash/pound.
I remember writing shell scripts with comments that appeared with the £ symbol at the front. In hindsight, it must have looked very strange, but at the time, it was just normal.
When 8-bit ascii with extended character sets started being used, life was a nightmare, because the number of different code-pages (CP437 and ISO8859-1 and -15 anybody) proliferated, with different code pages on different devices, making inter-operabillity extremely difficult.
I don't know how other OS's dealt with this, but IBM came up with quite complicated input and output methods on AIX for most devices that allowed you to specify a translation table that could be used to make it all work, but setting these up was quite complicated, and not many customers actually used them correctly (or in some cases, at all!)
It was only the adoption of various Unicode UTF character encoding schemes that things started working a little easier.