The Grassmarket area is first recorded in the fourteenth century, when it was referred to as ‘the street called Newbygging under the castle’. By the 1470s the area was known as ‘Westirmart’, and seems to have been associated with the sale of timber, hats, and shoes. At the far end of the Grassmarket stood the gateway known as the West Port, which was in existence by at least 1509, and formed the western boundary of the burgh.
The Canmore entry for Grassmarket is here.