engine
1. A piece of {hardware} that encapsulates some
function but can't be used without some kind of {front end}.
Today we have, especially, "{print engine}": the guts of a
{laser printer}.
2. An analogous piece of software; notionally, one that does a
lot of noisy {crunching}, such as a "database engine", or
"{search engine}".
The hackish senses of "engine" are actually close to its
original, pre-Industrial-Revolution sense of a skill, clever
device, or instrument (the word is cognate to "ingenuity").
This sense had not been completely eclipsed by the modern
connotation of power-transducing machinery in {Charles
Babbage}'s time, which explains why he named the
stored-program computer that he designed in 1844 the
"{Analytical Engine}".
[{Jargon File}]
(1996-05-31)