What is the origin of the word shit and does it have any relation to shi’ite muslims? If it does it still considered offensive to muslims a bit like wop, nip and nigger would be?
There is no connection between shit and Shia, so no offence is likely.
Shit is a very old word with Indo-European cognates up the wazoo, and dating back a thousand years or more in English.
Just to answer the first part of your question properly, the American Heritage Dictionary has shit<-Middle English shiten<-Old English *scitan (the star means this form is not attested but postulated). It is from a Proto-Indo-European root skeid meaning cut or split, and giving us all sorts of nice words like ski, science, shin and nice.
Shi’ite, or Shiite, Muslims are also called Shia. I am not an Islamic scholar, but I believe that in an earlier time, these Muslims were known as Aliid, or maybe Ali’id.
Someone with more knowledge can clear this up better, but this one of the main branches of Islam believes that the general leadership of the church should be inhereted through the descendants of the prophet Mohammed {Peace Be Upon Him], which would be via his nephew Ali (hence Ali-id); the other main branch (and please forgive the over-simplification) sort of thinks religious affairs should be directed via what I reckon in western terms would be like a council of Bishops, the Bishops getting their postitions through merit and ability rather than just blood relation to the Prophet. These would be the Sunni Muslims.
Muslims: Please don’t take offense at the over-compression of the history of Islam and its tenets.
IMHO, at least part of the confusion name-wise comes from no general agreement as to how Arabic characters should be transliterated into Roman characters. Reference the SD column of some years ago about the correct/accepted spelling of the name of Lybia’s present leader.
It’s not offensive to shiitake mushrooms, either.
The American Heritage Disctionary notwithstanding, (I ndon’t trust that “postulated form”), I’ve always felt that “shit”, like “fart” (the subject of another recent thread) is onomatopoeic as well. But I haven’t researched the matter.
what about “wank”?
Sitting next to a large monolith, an ape smashed a dessicated pig rib with a femur, sending it flying up into the air.
When it came down making contact with the ape’s head, the word “shit” was born.
Next?
“Origin unknown” per the OED, but the first cite is from 1948.
You may not have researched the matter, but you may want to see a doctor. 
If ya think about it, it was probably Noah. All those animals, and since it was already called a poop deck, he had to come up with something else. 'Course, I’m an atheist, so that makes absolutely no sense to me. Probably the guy that discovered fire. I think his name was Oooog.
Cassell’s Dictionary Of Slang gives the first use of wank as a noun to the 1940’s, which agrees with JeffB’s source.
The same work of reference gives the first use of wank as a verb to the late 19th century. It continues:
Etymology unknown but note the many beating synonyms, the original spelling whank and late 18th century Scottish dialect whank to beat or to thrash.
Shit if I know.
Sorry.
Which is exactly where you’d expect to find them.
[sub]Sorry, this cracked me up.[/sub]