I’m sure you’re familiar with the stagy way people sometimes pronounce the word ‘murder’
Here’s Frasier saying it Frasier - Murder most foul - YouTube
Is there a specific origin for this way of emphasizing the word - Basil Rathbone perhaps? Any ideas.
(note, the SDMB did do a good job with the similar question about Dracula Why Do Vampires Say "Bleh?" - Mundane Pointless Stuff I Must Share (MPSIMS) - Straight Dope Message Board)
Cheap stage melodramas is where that comes from.
Not the first, certainly, but a memorable one…Peter Lorre’s Joel Cairo in The Maltese Falcon (1941).
Spade is talking to the cops at his apartment door and has left O’Shaughnessy and Cairo together in the other room. She attacks Cairo somehow and the police enter. Cairo accuses O’Shaughnessy, saying “…I did not want to stay here and (eyes wide) be MOORDERED.”
Followed by the great throwaway line where Cairo prepares to leave along with the policemen and Spade asks where HE’S going. “oh, you, know…it’s late…” like he’s walking out on a tea party.
He’s quoting Shakespeare in the clip.
In the OP’s video, Frasier says, “murder most foul.”
This is a quotation from Shakespeare’s Hamlet (I.v.27-28), where the Ghost comments about his own death: “Murder most foul as in the best it is/But this most foul, strange and unnatural.”
Shakespearean actors often exaggerate the natural way of saying things for dramatic effect, as exemplified by the actor in this clip.