In the 16th Century the word 'mud' was used to describe anything
that was worthless and was linked with other English phrases such
as 'dragged through the mud - mud in your eye. In the 19th century
more phrases came into being, such as 'as thick as mud - as rich as
mud - as fat as mud'. It was only a matter of time before the word
was used in connection with someone's name. Thus an insult came
into being as 'your name is mud' meaning you are unpopular.