Quiz: Remember the definition of mal de mer?
word-forming element meaning "like, like that of, thing like a ______," from Latinized form of Greek -oeides, from eidos "form," related to idein "to see," eidenai "to know;" literally "to see," from PIE *weid-es-, from root *weid- "to see, to know" (see vision). The -o- is connective or a stem vowel from the previous element.
Resembling; one that resembles: cancroid.
A suffix meaning "like" or "resembling," as in ellipsoid, a geometric solid that resembles an ellipse.
[fr the scientific suffix -oid, fr Greek -oeides, ultimately fr eidos, ''image, form''; dictionaries list over 1,800 -oid compounds, most of which date from the 1700s and 1800s]
(from "android") A suffix used as in mainstream English to indicate a poor imitation, a counterfeit, or some otherwise slightly bogus resemblance. Hackers will happily use it with all sorts of non-Greco/Latin stem words that wouldn't keep company with it in mainstream English. For example, "He's a nerdoid" means that he superficially resembles a nerd but can't make the grade; a "modemoid" might be a 300-baud modem (Real Modems run at 144000 or up); a "computeroid" might be any bitty box.
"-oid" can also mean "resembling an android", which was once confined to science-fiction fans and hackers. It too has recently (in 1991) started to go mainstream (most notably in the term "trendoid" for victims of terminal hipness). This is probably traceable to the popularisation of the term droid in "Star Wars" and its sequels.
Coinages in both forms have been common in science fiction for at least fifty years, and hackers (who are often SF fans) have probably been making "-oid" jargon for almost that long (though GLS and ESR can personally confirm only that they were already common in the mid-1970s).