fine linen, fine hemp fiber
絺 centers on fine, high-quality plant fiber fabric: specifically fine linen or fine hemp fiber used for delicate cloth.
絺 combines 糸 (thread, fiber) with 希, which likely contributes the sound and may relate to the idea of fine or sparse threads. The exact historical development is uncertain.
The left side is thread 糸, and the right side 希 looks like a cloth with a cross pattern. Imagine weaving fine linen threads into a delicate, high-quality fabric.
For チ, picture a piece of fine linen so thin you can see through it like a sheet of cheesecloth: cheese -> チ, and the fine threads make the fabric.