I seriously believe its got to be of English origin in both tone and temperment. Maybe British with a hint of upper class jilt involved.
I see Sherlock jumping at the chance to use "Indubitably Mr. Watson" for the exact same reason someone today might say "No ** Sherlock."
But for Dr. Watson to say it, that means Sherlock would literally have to be in a coma for at least a couple of years to lose serious perspective and then having been awoken made a leap at something that used to be obvious that only now Dr. Watson has the upper had in understanding blusters out and stabs at a slowly awakening Sherlock and says something to the affect.
But what would Sherlock say to make Watson go into such a frenzy? "I think I'll have a cup of tea may haps?" No. Its more like Sherlock would say, "I think Moriarty tried to do me in."
Upon hearing such a thing Dr. Watson already knowing the answer full well after much investigating would leap at the chance, "All the clues were dangling over you like daggers Mr. Sherlock, surely!"