Felis domestica, a small animal that usually lives in house provided by its staff.
Felis Felis sylvestris catus, from an alternate (and detailed) phylogeny (at least you can see why cat). See http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Synapsida/Eutheria/Carnivora/Aeluroidea/Felinae.htm for more...
cat, a small utility that usually lives in bin provided by root's staff. PBO The name is said to be an abbrev. of concatenate, which is one of cat's uses.
Here's a partial reimplementation in Tcl from Playing Bourne shell (it does not write to stdout, but returns its results, for the caller to process further):
proc cat files { set res "" foreach file [eval glob $files] { set fp [open $file] append res [read $fp [file size $file]] close $fp } set res } ;# RS