Don, if you look at Snopes.com, and search for S.H.I.T., you'll find an item, a claim that this word is from the initial letters of "Ship High in Transit".
And Snopes says:
False.
Examples:
[Collected on the Internet, 2002]
History in the making!!!!
Fabulous bit of historical knowledge: Ever wonder where the word shit comes from ... well here it is
Certain types of manure used to be transported (as everything was back then) by ship ... well in dry form it weighs a lot less, but once water (at sea) hit it, it not only became heavier, but the process of fermentation began again, and one of the by products is methane gas . . . and as the stuff was stored below decks in bundles you can see what could (and did) happen, methane began to build up below decks and the first time someone came below at night with a lantern . . . BOOOOM! Several ships were destroyed in this manner before it was discovered what was happening. After that the bundles of manure where always stamped with the term S.H.I.T on them which meant to the sailors to "Ship High In Transit". In other words high enough off the lower decks so that any water that came into the hold would not touch this volatile cargo and start the production of methane.
Bet you didn't know that one.
I won't give you their essay which blows this one out of the water. If you are interested, I suggest you go to Snopes.com, search for "S.H.I.T.", and read the highly interesting explanation.