How should "aargh" really be pronounced?

The common interjections "argh!", "aargh!", "aaargh!", etc., is pronounced, as far as I know, the same as "aaa!" For most of my life, however, I (and I imagine many other second language speakers) pronounced it due to its spelling with an audible 'r' and hard 'g', and still do occasionally. In fact, I think this mispronunciation is so common that it has become an accepted alternative, especially when the word is used in humour (as opposed to genuine fright.) I often hear this version from native English speakers.

Questions:

  1. Is "aaa!" really the correct pronunciation?
  2. Why exactly is it spelled with the "rgh"? What purpose do those letters serve?
  3. If you agree that the mispronunciation has become an accepted alternative, can you think of any other cases where a mispronunciation gradually supplants or supplements the original? (Especially where this is caused by the eccentricities of English spelling and pronunciation.)

Solution 1:

My online dictionary shows that aargh is pronounced with the "r" sound, and either with a hard "g" or a silent "g" at the end.

I imagine that's the point of the "h" - to allow the "g" to go silent.

aargh |är; ärg| (exclamation) used as an expression of anguish, horror, rage, or other strong emotion, often with humorous intent.

Solution 2:

Regarding your question #3, I have heard people say "tisk, tisk" when mock-scolding. This comes from the written form "tsk, tsk" which is itself a representation of the dental click sound, used by many English speakers, signifying disapproval.