Source : Free On-Line Dictionary of Computing

microtape
     
         /mi:'kroh-tayp/ Occasionally used to mean
        a {DECtape}, as opposed to a {macrotape}.
     
        Apparently the term "microtape" was actually the official term
        used within DEC for these tapes until someone coined the word
        "DECtape", which, of course, sounded sexier to the
        {marketroid}s.  Another version of the story holds that
        someone discovered a conflict with another company's
        "microtape" trademark.
     
        [{Jargon File}]
     
        (1995-03-16)