In Victor Canning's 1950 Bird of Prey, I encountered this sentence:
Spadoni nodded, his eyes dropping from Mercer's face, taking in the tweed jacket with leather-bound cuffs, the neatly pressed gray trousers with the virtue long gone from the flannel and the well-worn, highly-polished shoes.
As it should be, the general meaning of 'virtue' in this context is clear; however, I felt there must be a more specific meaning I was missing. As a metaphor, the use is understandable but general, and encompasses everything about 'the excellence of new flannel'. This did not seem sufficient to explain the use, but perhaps it is sufficient.
I searched the OED for some specific definition of 'virtue' pertaining to a quality of new as opposed to old cloth, and hoping for something pertaining particularly to flannel, with no good result.
Is there a definite virtue, unique to flannel, that is lost with age? Was or is this a description of flannel specific to a particular quality, or a general metaphor that might be applied to any cloth?