Carpenter's Wood Filler.

As a note: I would have Carpenter's Wood Filler be the primary definition entry for these, and refer FnF and Fill and Finish back to it.  FnF is not a term that the Elmer's product uses, and in fact there are different products called Fill 'n' Finish although many folks still seem to use the term to refer to CWF.

CWF seems to be the more correct term right now.