type of tall evergreen tree
梛 refers to a specific type of tall evergreen tree, with no extended abstract meanings.
梛 combines 木 (tree) with 那, which likely contributes the sound. The character was created to name a particular tree species.
The left side 木 is a tree, and the right side 那 looks like a tall, spreading shape. Picture a towering evergreen with branches spreading out like the strokes of 那.
For ダ, imagine a tall evergreen tree casting a dark shadow: dark -> ダ, and the tree's shade is as dark as its dense foliage.