FBI is pronounceable. Part your lips slightly and say with me 'eff bee eye'. It is an acronym, see?

I hear that S**T is an acronym for 'Store High In Transit', coined during some era, in reference to cow dung that was previously stored below deck during sea-travel. The gasses from the damp cow-dung would cause an explosion when you went down there with an open-flame lamp.

After suffering this for a bit, some smart person figured it out and decided that all cow dung would be Stored High In Transit from then on. Hence, S**T.

Probably a load of horse s**t but I like it.