bier, coffin
柩 centers on a container for the dead: a bier or coffin used in funeral rites.
柩 combines 木 (wood) with 匛, which likely contributes the sound and relates to a container. The character originally referred to a wooden coffin or bier.
The left side is 木 (wood), and the right side 匛 looks like a box with a lid. Picture a wooden box used as a coffin or bier.
For キュウ, imagine a queue of mourners carrying a wooden coffin: queue -> キュウ, and the coffin is made of wood.