frobnitz: /frob'nits/, plural `frobnitzem' /frob'nit-zm/ or `frobni' /frob'ni:/ [TMRC] n.

:frobnitz: /frob'nits/, plural `frobnitzem' /frob'nit-zm/ or
`frobni' /frob'ni:/ [TMRC] n. An unspecified physical object, a
widget. Also refers to electronic black boxes. This rare form is
usually abbreviated to `frotz', or more commonly to {frob}.
Also used are `frobnule' (/frob'n[y]ool/) and `frobule'
(/frob'yool/). Starting perhaps in 1979, `frobozz'
/fr*-boz'/ (plural: `frobbotzim' /fr*-bot'zm/) has also
become very popular, largely through its exposure as a name via
{Zork}. These variants can also be applied to nonphysical
objects, such as data structures.

Pete Samson, compiler of the original {TMRC} lexicon, adds,
"Under the TMRC [railroad] layout were many storage boxes, managed
(in 1958) by David R. Sawyer. Several had fanciful designations
written on them, such as `Frobnitz Coil Oil'. Perhaps DRS intended
Frobnitz to be a proper name, but the name was quickly taken for
the thing". This was almost certainly the origin of the
term.
-- The AI Hackers Dictionary