‘Cad’ means a junior assistant or odd-job man.
Governor MacGregor was indeed a ‘great sufferer from old wounds’. The Clan Macfarlane website relates that ‘he was wounded in seven places when treacherously attacked, with his own sword sheathed, while receiving the surrender of Fort Talneir in India in 1818: receiving severe kris wounds in the left shoulder, left side, and in two places ...