The word "sunblock" is a modern English compound, transparently formed from the native Germanic elements "sun" and "block." The logic is entirely literal: a substance that blocks the sun. The term emerged in the mid-20th century alongside increased public awareness of the dangers of ultraviolet radiation. Unlike opaque or classical compounds, its meaning is directly accessible from its parts, representing a practical, descriptive approach to naming a consumer product designed to physically obstruct harmful solar rays from reaching the skin.

Structure: sun (star) + block (obstruct) - sun: From Old English sunne, of Germanic origin. In this compound, it functions as a noun denoting the celestial body whose rays are being obstructed. - block: From Middle English blok, from Old French bloc, of Germanic origin. In this compound, it functions as a verb-derived element meaning to stop or obstruct.