When Dr Enys is attending Caroline Penvenen he asks Ray Penvenen to bring him a glass of warm salt water. To which Ray Penvenen replies "I'll have it bought up dreckly" with a sense of urgency, Implying that it will be bought up as soon as possible. "Dreckly" is an old Cornish dialect word still in use today that means "at some unspecified point in the future, but not immediately". This does not match the implied meaning in the scene.
Demelza uses the expression: 'give me the cold shoulder', which first appeared in print ( in the Scots language ) in 'The Antiquary' by Sir Walter Scott in 1816 and so it's unlikely it would have been known of or used in Cornwall half a century before then.