As has been recounted elsewhere in this site, there are a number of explanations for origins of the name "Buccleuch". Suffice to say here that the name was adopted by the Scott family that established themselves in the Scottish Borders west of Hawick and became one of the most powerful and wealthy in the region.
But although the Duke of Buccleuch is a prominent name in Scotland, the use of "Buccleuch" as a surname is not widespread in this country. Indeed, Dr George F Black's reference work on Scottish surnames which covers over 8,000 Scottish family names does not even have an entry for "Buccleuch".
But the name Buccleuch - and a number of variants including in particular Buckaloo and Bucklew (bearing testimony to the way the name must have sounded to the officials at the immigration entry points into the USA) have become quite widespread in North America in particular. Naturally, they have been welcomed into the Scott clan / family.