wwh pointed me at an earlier thread on pure as a noun meaning dog dung.

http://wordsmith.org/board/showthreaded.pl?Cat=&Board=beheadingwords&Number=85701

Interesting. The OED derives pure 'dog's dung or other substance used as an alkaline lye for steeping hides (in leather making)'. Also spelled pewer or puer. I think that the puer spelling may have suggested boys, pueri in Latin, but the meaning is from Latin purus 'pure, clean'. Under pure as a verb, is a quotation: "Bating or puring as it is called, is a process by which all but a very small amount of the natural grease is removed from the skin."