Origin and history of exceptionable

late 14c., excepcioun, "the act or fact of leaving out or the excluding of" from the scope of some rule or condition, from Anglo-French excepcioun (late 13c. in a legal sense, "formal objection or protest entered by a defendant"), Old French excepcion, from Latin exceptionem (nominative exceptio) "an exception, restriction, limitation; an objection," noun of action from past-participle stem of excipere "to take out" (see except).

From c. 1400 as "a reservation or exemption;" from late 15c. as "something that is excepted." The figure of speech in to take exception "find fault with, disapprove" is from excipere being used in Roman law as a modern attorney would say objection.

The exception that proves the rule is from law: exceptio probat regulam, short for exceptio probat regulam in casibus non exceptis, "the exception proves the rule in cases not excepted," also given in other similar wordings, said to be from Cicero. Exception here is "action of excepting" someone or something, not the person or thing that is excepted, and prove is "put (the rule) to the test, examine the truth of."

An item in "Notes & Queries" [F.C. Birkbeck Terry, July 1, 1893] points out the legalese origin, adding, "But scientific exactness now treats the question in another way." The shift was noted by the Rev. H. Percy Smith ("Glossary of Terms and Phrases," 1885), who defined the common understanding of exception proves the rule as "the fact of there being an exception proves the existence of a rule," or "an exception is essential to every rule."

But Smith noted that, properly, it means, "A special exception to a rule proves it to hold concerning things not specially excepted."

"justly liable to objection, calling for disapproval," 1779, from objection + -able. Related: Objectionably.