Just came across a version of Dame Durden printed in 1858 - and it looks like the version we know has been cleaned up a little!
(I did check and couldn't find this version here)

Last verse:

'Twas on the morn of Valentine
The birds began to prate
Dame Durden's servants, maids and men
They all began to mate (!)

Dame Durden, The book of popular songs ed J. E. Carpenter, pp 60-61