From The Free On-line Dictionary of Computing (19 Sep 2003) [foldoc]:
automagically
<jargon> /aw-toh-maj'i-klee/ or /aw-toh-maj'i-k*l-ee/
Automatically, but in a way that, for some reason (typically
because it is too complicated, or too ugly, or perhaps even
too trivial), the speaker doesn't feel like explaining to you.
E.g. "The C-INTERCAL compiler generates C, then automagically
invokes cc to produce an executable."
See magic.
[Jargon File]
(2001-05-18)
From Jargon File (4.4.4, 14 Aug 2003) [jargon]:
automagically
/aw.toh.maj'i.klee/, adv.
Automatically, but in a way that, for some reason (typically because
it is too complicated, or too ugly, or perhaps even too trivial), the
speaker doesn't feel like explaining to you. See magic. "The
C-INTERCAL compiler generates C, then automagically invokes cc(1) to
produce an executable."
This term is quite old, going back at least to the mid-70s in jargon
and probably much earlier. The word `automagic' occurred in
advertising (for a shirt-ironing gadget) as far back as the late
1940s.