Expansion of the acronym "grep"

[glass at mica.berkeley.edu]

What is the correct expansion of the acronym "grep"? I'm told that this
has come up in comp.unix.questions before, but the relevant articles are
no longer on my news server. I'd also be interested in knowing what the
acronyms for the other flavors of grep (e.g. egrp) expand to.

--Brett

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"One of the nicest things about mathematics, or anything else you might
 care to learn, is that many of the things which can never be, often are."
                                      Norton Juster, "The Phantom Tollbooth"
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