noun
shade of a rock; shelter behind a rock
Refers to the shadow or sheltered area behind or under a large rock, often implying a hidden or protected spot.
彼は岩陰に隠れて、追っ手が通り過ぎるのを待った。
He hid in the shade of a rock and waited for his pursuers to pass.
海岸で岩陰に小さなカニがたくさんいた。
There were many small crabs in the shelter of the rocks at the beach.
Compound of 岩 (iwa, 'rock') and 陰 (kage, 'shade; hidden place'). The reading いわかげ is a straightforward combination.