Germanic *handuz and Latin manus spent millennia in contact yet chose entirely different names for the tool that makes every other tool. Chinese 手 bypasses the argument: it is a drawing of a hand, fingers still legible in three-thousand-year-old brushwork. Esperanto chose the Roman form, quietly binding its speakers etymologically to Spanish and away from the Germanic north. Four words, no common lineage — all reaching toward the same warm, outstretched fact.
A proposed connection to PIE *ghend- 'to seize' (which also underlies Latin prehendere) exists in the literature but is not universally accepted; treat as speculative.
Latin manus was third-declension feminine; Spanish preserves this as a conspicuous exception — mano is one of the very few Spanish -o nouns that remains grammatically feminine (la mano, never *el mano).
An oracle bone pictograph of an open hand seen from the front: five digits splayed above a palm. Three thousand years of brush and chisel compressed this into four strokes, but the silhouette of the spread hand remains legible. As a radical (手旁), it seeds hundreds of characters for every action a hand performs — grasping, striking, lifting, writing.
手 is a pure pictograph (象形字) and does not carry semantic component structure in the way compound characters do; the decomposition above describes pictographic elements, not logical radicals. In its compressed left-side radical form it becomes 扌.
Productive compounds: manpremo (handshake, 'hand-press'), manskribo (handwriting, 'hand-writing'). Notably, the related body-vocabulary splits sources: polmo (palm) comes from Latin palma, while fingro (finger) derives from Germanic *fingraz — Esperanto's hand vocabulary straddles both Roman and Germanic traditions in a single register.
Every civilization drew a hand in the dirt before it had a word for one — and in Chinese, the drawing never fully stopped.