Source : Free On-Line Dictionary of Computing

lost in the underflow
     
         Too small to be worth considering; more specifically,
        small beyond the limits of accuracy or measurement.  This is a
        reference to "{floating point underflow}".
     
        The {Hacker's Jargon File} claimed that it is also a pun on
        "undertow" (a kind of fast, cold current that sometimes runs
        just offshore and can be dangerous to swimmers).
     
        "Well, sure, photon pressure from the stadium lights alters
        the path of a thrown baseball, but that effect gets lost in
        the underflow".
     
        Compare {epsilon}, {epsilon squared}; see also {overflow bit}.
     
        (1997-09-05)