As an adult, I tend to think of "smut" in the production sense related to the grains; wheat, & barley.

http://scarab.msu.montana.edu/Disease/DiseaseGuidehtml/webFunghead.htm

As a child I tended to equate "smut", with risking a bar of Ivory soap in the mouth

jh

"It's not what I say that's important, it's what you hear" Red Auerbach