Leonard Erickson wrote in a message to Lance Lyon:

 LE> The "2 = ABC" etc stuff is a carryover from the old named exchanges
 LE> stuff that dates back to the 1920s on dial telephones. And
 LE> different countries assign those differently. It looks like
 LE> Australia uses the same assignments for those as the US does.

 LE> But the A, B, C, and D tone pairs have nothing to do with those old
 LE> mnemonics. 

Heck,  I'm probably dating myself here but I remember those named
exchanges. There was a big deal in certain areas of NYC to have one of
certain ones,  it was a "prestige" thing...   I also remember
running across some stuff where there were only four digits rather than
five following the exchange.  And I recall a big deal in the phone books of
the day that made it a point to tell the customer that 0 and O were not the
same,  as were 1 and I.  

These days I guess it's more a matter of sometimes people getting a number
that they can make something out of,  so they can use it in advertising.
Supposedly this makes it easier to remember.  To me they were always a pain
in the butt, and I'd translater it to straight numbers before I'd attempt
to dial it -- just out of the habit of using those letters,  I suppose.

I also remember running across a computer program that'd give as output a
list of all possible "words" that you could get from any given
phone number.  Might even still have that around someplace,  though I don't
think it'd be too hard to write such a thing.

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