Question on a 19th century English phrase:

In my researchers for a book I have come across this phrase written in July 1839

'Mr Tatton is certainly a liberal radical mountebank and five legged bastard'.

Okay what is the meaning of a 'five legged bastard'?

Biblical? What? Some odd British thing? Stallion?

TIA

via International Skeptics Forum http://ift.tt/2EI7MZj