Surprised no-one's mentioned "sharp" yet, as in the musical symbol which is almost - but not quite - the same shape.
I, too, always assumed that #="pound" was just one of those things because US and UK keyboards differed, but if it might have been "gate" then maybe pound could be because it looks a bit like a fenced-off area :-)
"Pling" was common in the 1980s ISTR. I think I first came across it when Acorn-types needed a quicker way to pronounce the indirection operator ("?" was used for bytes, "!" for 16 bits IIRC) and started using "query" for "question mark".
Also, going back to the Bell thing, the 10+2 telephone keypad was actually a subset of the DTMF thing, I think. DTMF had (as the name implies) two tones. Each tone had four frequencies for a total number of combinations of 16. 12 (3x4) were used in the telephone keypad and the other four (ABCD?) did "other things" if you could generate them...
Just vague memories, quite possible entirely wrong :-)