Based on my knowledge, the second-largest Scottish island with 4 letters is Skye.
Skye is an island in the Inner Hebrides of Scotland. It is the largest island in the Inner Hebrides and the second largest island in Scotland after the Isle of Lewis and Harris. Skye is known for its dramatic scenery, including mountains, cliffs, and waterfalls. The island is also home to a number of historical and cultural attractions, such as Dunvegan Castle and the Kilt Rock.
Here are some other Scottish islands with 4 letters:
- Mull
- Islay
- Jura
- Coll
- Tiree