I laughed when I first saw the arglist for R6RS's
(error who msg irritant1 ...)
There are irritants in the Scheme oyster, and
error pearls them away for later reference. Cute!
“Irritant” is not a new term; it's existed in Scheme culture for a long time. The earliest reference I can find is in a Maclisp Scheme info file last modified in 1985, and it has turned up occasionally on the rrrs-authors mailing list. I haven't found it in any non-Scheme manuals (yet). Is it a Scheme-only term? Does anyone know where it originated?
For a while, the cuteness blinded me to a possible confusion: “irritants” suggests that the arguments should be the cause of the error — that they should be in some sense wrong or invalid. But they're only informative, and are often innocent indicators, not the causes of the irritation.
format string and arguments is probably better, because it makes clearer messages. Or simply a string, in a language with string interpolation. Even though this doesn't call for a cute name.