The
sgian-dubh may have evolved from the
sgian-achlais, a dagger that could be concealed under the armpit. Used by the Scots of the 17th and 18th centuries, this knife was slightly larger than the average modern
sgian-dubh and was carried in the upper sleeve or lining of the body of the jacket.
[2]
Courtesy and
etiquette would demand that when entering the home of a friend, any concealed weapons would be revealed. It follows that the
sgian-achlais would be removed from its hiding place and displayed in the stocking top held securely by the
garters.
[3]
https://en.wikipedia.org/wiki/Sgian-dubh
The Scots have pride in the strength & thickness of their kilt hose.