Sgian dubh = black knife

Long one is called Dirk.

Yes, in your luggage and declared at Customs.

It's called a sgian dubh (pronounced skin doo)

The most common term for a dagger in Gaelic is "Sgian Dhubh" which actually translates as "black knife" This is a small dagger which is traditionally worn at Scottish Weddings in the side of the Kilt sock worn by the male members of the wedding party. The word "Sgian" is probably the closest translation to dagger. The Scottish Gaelic word is biodag (dagger, dirk).

Knives are dangerous things and should not be bought by minors and so you cannot buy them online. You are better off going to a home store and going to the kitchen section.