why didn't you warn me about the dog s***?

The word "shit" has been used as an expletive for many years, and through over use has lessened in its intensity and shock value. It is also used quite widely as a term for general mess, and in several other phrases. However, its use as a term for excrement seems to have a higher intensity and is eschewed (No - I already saw that joke, thank you) - in polite company. Hence I have heard a polite lady state "Oh shit! I just stepped in some doggy doo-doo".
Is there a name for this process? Can you think of some other examples? I'm not trying to trawl the gutter, just trying to explore this phenomenon.

Rod