Interesting. The Jewish equivalents of kosher (proper), parve (neutral) or treif (bad) also originally only applied to food (Kashrut dietary laws), but going as far back as the 3rd century, kosher came to mean "virtuous." It is pretty easy jump once you start talking about utensils used for food being kosher or not.
Reverse Influence from Christianity perhaps? I may have lost the faith - but I've always liked the following as a religious statement: (From Matt 15 / ESV)
You are still no more intelligent than the others.17 Don't you understand? Anything that goes into your mouth goes into your stomach and then on out of your body.18 But the things that come out of the mouth come from the heart, and these are the things that make you ritually unclean.19 For from your heart come the evil ideas which lead you to kill, commit adultery, and do other immoral things; to rob, lie, and slander others.20 These are the things that make you unclean. But to eat without washing your hands as they say you should—this doesn't make you unclean.
