 Since at least the 14th century , Thomas Becket , Archbishop of Canterbury has been attributed a coat of arms consisting of three Cornish choughs on a silver field . The symbolism behind this is not known for certain ; according to one legend , a chough strayed into the cathedral during Becket 's murder , while another school of thought states that the choughs are a canting reference to Becket 's name , as they were once known as " <unk> " . The latter theory does not stand up to scrutiny , as the use of the term " <unk> " to mean a chough is not found before the 19th century . Regardless of its origin , the chough is still used in heraldry as a symbol of Becket , and appears in the arms of several persons and institutions associated with him , most prominently the city of Canterbury . 
