The term appears to have originated in the FreeBSD community, and now stands for any topic which causes heat out of all proportion to its importance.
Explanation from FreeBSD FAQ:
For the original post, see: Too dull, maybe? Don't like beige? etc. ad nauseam.WadlersLaw is the corollary for ProgrammingLanguage design.
A bike shed is a shed that contains bikes (obviously).
What's a "bike"? What's a "shed"? In what sense do you mean "contain"? What do you call an empty "bike shed"?
Personally, I prefer to use database tables to store my bikes in. They just map more naturally to my mental processes. I demand seven concrete reasons why you use a shed instead of a database table.
Well, welcome to wiki, where sheds are made of tables, reasons are made of concrete and assuming meaningful meaning means you don't understand what I meant.
See also MeaningDependsOnContext, WadlersLaw