patois
Concise Oxford English Dictionary © 2008 Oxford University Press:
patois /ˈpatwɑː/
▶noun (pl. same /-wɑːz/) the dialect of a particular region, especially one with low status in relation to the standard language of the country.
– origin C17: Fr., lit. ‘rough speech’, perh. from OFr. patoier ‘treat roughly’, from patte ‘paw’.
'patois' also found in these Oxford entries:

