The Collaborative International Dictionary of English v.0.48:

Ampersand \Am"per*sand\, n. [A corruption of and, per se and, i.
   e., & by itself makes and.]
   A word used to describe the character ?, ?, or &.
   --Halliwell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ampersand
    n 1: a punctuation mark (&) used to represent conjunction (and)

The Free On-line Dictionary of Computing (30 December 2018):

ampersand
&
amper

    "&" ASCII character 38.

   Common names: ITU-T, INTERCAL: ampersand; amper; and.
   Rare: address (from C); reference (from C++); bitand;
   background (from sh); pretzel; amp.

   A common symbol for "and", used as the "address of" operator
   in C, the "reference" operator in C++ and a bitwise and
   or logical and operator in several programming languages.
   Visual BASIC uses it as the string concatenation
   operator and to prefix octal and hexadecimal numbers.

   UNIX shells use the character to indicate that a task
   should be run in the background (single "&" suffix) or
   (following C's lazy and), in a compound command of the
   form "a && b" to indicate that the command b should only be
   run if command a terminates successfully.

   The ampersand is a ligature (combination) of the cursive
   letters "e" and "t", invented in 63 BC by Marcus Tirus [Tiro?]
   as shorthand for the Latin word for "and", "et".

   The word ampersand is a conflation (combination) of "and, per
   se and".  Per se means "by itself", and so the phrase
   translates to "&, standing by itself, means 'and'".  This was
   at the end of the alphabet as it was recited by children in
   old English schools.  The words ran together and were
   associated with "&".  The "ampersand" spelling dates from
   1837.

   Take our word for it
   (http://takeourword.com/Issue010.html).

   (2012-07-18)