"Cockburn, at the Moat house, Chepstow...
- I know that fellow, says Joe, from bitter experience.
- Cockburn." (U12.231)
W. Cockburn M.D. was the author of "The Symptoms, Nature, Cause and Cure of a Gonorrhoea" in the 18c. Could that be the reason Joe is familiar with the name? (Suggested by Harald Beck)