River Ettrick, river, Scottish Borders council area, Scot. The River Ettrick, noted for its trout and salmon, rises in the extreme southwest of the district and flows northeast for 32 miles (51 km) to the River Tweed. Its valley, Ettrickdale, has literary and family connections with Sir Walter Scott. Buccleuch, a stronghold that gave another Scott family the titles of earl (1619) and duke (1663), is nearby.