6. (booksellers’).—To stain; to discolour with damp; said of books and
engravings. Foxed = stained or discoloured.
1881. C. M. I[ngleby] in Notes and Queries (6th S., iv., 96).
Tissue paper harbours damp, and in a damp room will assuredly help
to fox the plates which they face.
1885. Austin Dobson, At the Sign of the Lyre, 83. And the Rabelais
foxed and flea’d.