Source : Free On-Line Dictionary of Computing

beta testing
     
         Testing a pre-release (potentially unreliable)
        version of a piece of software by making it available to
        selected users.  This term derives from early 1960s
        terminology for product cycle checkpoints, first used at {IBM}
        but later standard throughout the industry.
     
        "{Alpha test}" was the unit, module, or component test phase;
        "Beta Test" was initial system test.  These themselves came
        from earlier A- and B-tests for hardware.  The A-test was a
        feasibility and manufacturability evaluation done before any
        commitment to design and development.  The B-test was a
        demonstration that the engineering model functioned as
        specified.  The C-test (corresponding to today's beta) was the
        B-test performed on early samples of the production design.
     
        An item "in beta test" is thus mostly working but still under
        test.  In the {Real World}, systems (hardware or software)
        often go through two stages of release testing: Alpha
        (in-house) and Beta (out-house?).  Beta releases are generally
        made available to a small number of lucky (or unlucky),
        trusted customers.
     
        (1996-11-05)