Toward the end of this long thread from February, we got onto the subject of the symbol # being used for pounds; I had never seen it, but was presented with enough convincing evidence that I threw up my hands and accepted it (“Huh, you learn something every day. I wonder how I managed to miss the # = lb. thing?”). Now Mark Liberman at the Log has a post on this very topic:
Yesterday, in discussing Kevin Fowler’s song Pound Sign, there was some debate about the origin of the term “pound sign” for the symbol #. I suggested that it all started with the substitution of # for £ on American typewriter keyboards, but others argued that # was a standard symbol for pound(s) avoirdupois. I’ve heard this theory before, but I expressed skepticism about it because I’ve never actually seen the symbol used that way.
I’m not clear on why he’s so much more stubborn than me about accepting this use of the symbol, since he finds examples going back to 1923 and his commenters are as adamant about being familiar with it as mine, but he comes to this conclusion: “So I’m quite sure that this is why the engineers at Bell Labs called # “pound sign” — it corresponded to a Baudot code-point that had been used for £ in the UK and # in the U.S., probably since the late 19th century and certainly since the early 20th century.” You can find out about Baudot code-points in his post, and there’s already a lively discussion going on. (And that “Pound Sign” song is a lot of fun too.)