The Jargon File (version 4.4.7, 29 Dec 2003):

UUOC


    [from the comp.unix.shell group on Usenet] Stands for Useless Use of cat;
    the reference is to the Unix command cat(1), not the feline animal. As
    received wisdom on comp.unix.shell observes, ?The purpose of cat is to
    concatenate (or ?catenate?) files. If it's only one file, concatenating it
    with nothing at all is a waste of time, and costs you a process.?
    Nevertheless one sees people doing


    cat file | some_command and its args ...

    instead of the equivalent and cheaper