壳 has two pronunciations: ké (colloquial, used in daily speech like 蛋壳, 贝壳) and qiào (more formal/literary, used in compounds like 地壳 dìqiào 'earth's crust'). In everyday use, ké is far more common.
memory
Think of cracking open a nut — 壳 is the outer covering you break through to get to the good stuff inside.
Xinhua indexes 壳 under the 士 (scholar) radical at the top. Pedagogically this is a radical-exposure pick rather than an etymological one: the original 殼 pictured a hand striking a pottery vessel. The simplified silhouette has converged on a clean 士 cap that anchors lookup.
The lower four-stroke unit is 冗 — a roof over a small figure. In 壳 it pictures the curved shell or husk hollowed out beneath the cap, the enclosed space from which something emerges. Compare the 冗 silhouette in 沉 and other roofed bodies.
