french letters...

[Bradley O'Neill]

I post the following trivial question here, as I am more likely to get a
snappy answer from a Pynchon-wonk than from anyone else. So,
encyclopedists, activate:

        **What is the origin of the term 'french letters' for condom?

If you know the answer, or don't *know* but have a clever idea, fill me in.
I apologize to those readers whose bandwidth sensibilities I may have
offended...

Regards,

Bradley.