Pros from Dover

[Michael Quinion]

A subscriber has asked about "pros from Dover", which he has found
in the Tom Clancy book "Rainbow Six" and which seems to mean
experts. I know that it was used in the 1970 Robert Altman film
M*A*S*H. Can anyone take it back further or give me a pointer to
where it might have come from?

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Michael Quinion
Editor, World Wide Words
E-mail: <TheEditor at worldwidewords.org>
Web: <http://www.worldwidewords.org/>