This article is from the alt.usage.english FAQ, by Mark Israel firstname.lastname@example.org with numerous contributions by others.
(The lists of names given in this entry are DELIBERATELY
incomplete. For a comprehensive list of formal and informal terms
for these and many other keyboard symbols, see the entry ASCII in
the Jargon File.)
"&" is called "ampersand".
The longest name for "@" is "commercial at sign"; the first and
last words may each be omitted. The official ANSI/CCITT name is
There are actually two typeset symbols, with distinct histories,
for which we use "#" in ASCII text.
One (with horizontal strokes slanted and thicker than the
vertical strokes) is the musical "sharp (sign)", as in "the key of
The other (with vertical strokes slanted) is called "number
(sign)", as in "the team finished in the #5 position", or "pound
(sign)", referring to weight, as in "a 5# bag of potatoes".
Although use of this sign to denote weight has declined, "pound" is
the most widely used name for it in the U.S. But it confuses people
who expect that term to mean the symbol for sterling currency
(located on many British keyboards in the same place as "#" is found
on U.S. keyboards). "Number sign", adopted by ANSI/CCITT, is
unambiguous, but little known in both the U.K. and the U.S.
Computer-users in the U.K. usually call the symbol a "hash", from
its appearance (reminiscent of marks one might make when chopping).
Finally, in a failed attempt to avoid the naming problem by
creating a new name, the term "octothorp(e)" (which MWCD10 dates
1971) was invented for "#", allegedly by Bell Labs engineers when
touch-tone telephones were introduced in the mid-1960s. "Octo-"
means eight, and "thorp" was an Old English word for "village":
apparently the sign was playfully construed as eight fields
surrounding a village. Another story has it that a Bell Labs
supervisor named Don MacPherson coined the word from the number of
endpoints and from the surname of U.S. athlete James Francis Thorpe.
Merriam-Webster Editorial Department told me: "All of the stories
you record are known to us, but the evidence does not line up nicely
behind any one of them."