A Legend of the Origin of the Naesmyth Family Surname

The following is one of the family legends of the origin of the name of Naesymth:-- (Extracted from the Autobiography of James Hall Nasmyth)

In the troublous times which prevailed in Scotland before the union of the Crowns, the feuds between the King and the Barons were almost constant.  In the reign of James III the House of Douglas was the most prominent and ambitious. The Earl not only resisted his liege lord, but entered into a combination with the King of England, from whom he received a pension.  He was declared a rebel, and his estates were confiscated.  He determined to resist the royal power, and crossed the border with his followers.  He was met by the Earl of Angus, the Maxwells, the Johnstons, and the Scots.  In one of the engagements which ensued the Douglas' appeared to have gained the day, when an ancestor of the Naesmyths, who fought under the royal standard, took refuge in the Smithy of a neighbouring village. The smith offered him protection, disguised him as a hammerman with a leather apron in front, and asked him to lend a hand at his work.

While thus engaged a party of the Douglas partisans entered the Smithy. They looked with suspicion on the disguised hammerman, who, in his agitation, struck a false blow with the sledge hammer, which broke the shaft in two.  Upon this, one of the pursuers rushed at him, calling out, "Ye're nae Smyth!"   The stalwart hammerman turned upon his assailant, and, wrenching a dagger from him, speedily overpowered him.  The Smith himself, armed with a big hammer, effectually aided in overpowering and driving out the Douglas men.  A party of the royal forces made their appearance, when Naesmyth rallied them, led them against the rebels, and converted what had been a temporary defeat into a victory.  A grant of lands was bestowed upon him for his service.  His armorial bearing consisted of a hand dexter with a dagger, between two broken hammer-shafts, and there they remain to this day.   The motto was, Non arte sect marte, "Not by art but by war".

This legend would seem to have a ring of truth about it since it hits so close to information we have been able to confirm.
First, the spelling of the name, Naesmyth in old Scottish would indeed mean "Not" (nae) and "Smith" (Smyth).  Or, "Not a Smith".
Secondly,  we do know that the Naesmyth Armorial Bearing contains a hand holding a sword and broken hammers.   Both of these objects can be explained by the above legend while it would be difficult to comprehend any other logical reason to have a broken hammer as your Arms (and Crest).
And, thirdly, The known Naesmyth Motto of "Non arte sect marte" (sometimes spelled - "Non arte sed marte") or "Not by art but by war" would again lend credence to this legend.  "Art" of course being the craft of the Smith and "War" as being the the true talents of our ancestor.

Although we cannot be sure that this is the true origin of our surname, it is not only a good story but quite viable as well.