Ireland: The A-Z Irish Glossary - 'K' is for 'Knacker'
'Knacker'
Originally, a person who deals in horses, particularly those in the
horse trade responsible for converting old horses into fertiliser
and adhesives.
Nowadays, the term has lost all descriptive meaning and
has become a generic term of abuse for anyone the speaker
a) has a problem with and
b) considers a good few rungs down the
social ladder from themselves, e.g. Scumbags
and Our friends in the travelling community.
A horrible derogative word, for such a pretty picture.