Recognised shorthand on the Usenet group comp.std.c for any

unexpected behaviour of a C compiler on encountering an

undefined construct. During a discussion on that group in

early 1992, a regular remarked "When the compiler encounters

[a given undefined construct] it is legal for it to make

demons fly out of your nose" (the implication is that the

compiler may choose any arbitrarily bizarre way to interpret

the code without violating the ANSI C standard). Someone

else followed up with a reference to "nasal demons", which

quickly became established.