The larger ones are dirks, the smaller are called sqian dubhs.
Heres a tid bit on the dirks
https://en.wikipedia.org/wiki/Dirk
And on the sqian dubhs a bit more:
https://en.wikipedia.org/wiki/Sgian-dubh
Many dirks were made from broken broadsword blades. Both will almost always have filework on the spine.
The sgian dubh was a utility knife. The dirk a weapon.
This painting below is very important historically. It shows the detail from the Battle of Culloden or Drummosie Moor as the Highlanders called it. The Highlanders being painted were prisoners after the battle. They were wearing their own clothes that they were wearing that day and given their pick of recovered weapons. Guessing the artist had some juice. Note the two in the center that are attacking with broadswords each have a dirk in their left hand under the targe (shield). Another interesting thing this painting tells us is the idea of clan tartans didn't exist at the time.