Back in the early 60's, touch tone phones only had 10 buttons. Some
military versions had 16, while the 12 button jobs were used only by people
who had "diva" (digital inquiry, voice answerback) systems -- mainly banks.
Since in those days, only Western Electric made "data sets" (modems) the
problems of terminology were all Bell System. We used to struggle with
written descriptions of dial pads that were unfamiliar to most people
(most phones were rotary then.) Partly in jest, some AT&T engineering
types (there was no marketing in the good old days, which is why they were
the good old days) made up the term "octalthorpe" (note spelling) to denote
the "pound sign." Presumably because it has 8 points sticking out. It
never really caught on.