The story
Supposedly proposed by programmer Ward Cunningham sometime in the early 1980s, but Cunningham himself denies having ever said it.
Etymology from Wiktionary, CC BY-SA 4.0.
Cunningham's Law
Today it means: A humorous law of Internet forums, stating that "The best way to get the right answer on the Internet is not to ask a question; it's to post the wrong answer." Full definition →