I got the following from:

members.aol.com/esarrett/pink/pink001.htm

The PINKERTON name is Norman in origin, being derived from the
name of a little place in the "Department of Orne" called Pont Chardon
(Thistle Bridge). Some early PINKERTON's have been recorded from
Scotland, of the old barony of PINKERTON near Dunbar, East Lothian.
NICOL de PYNKERTONE of Haddingtonshire, Scotland, rendered homage
in the year 1296.
(See Source: Bain, II pg. 210 ..prs)

His seal shows a mastiff barking, a rose above, S' Nicolai de Princriton
(ibid., pg. 544. ..prs)

PATRICK de PENKERTON had protection for a year in England
in the year 1396 (ibid., IV, 484.)