Quavering comes from Middle English quave ('to tremble') + the suffix -ing, giving quavering ('trembling or shaking'), now used of a trembling voice or sound. In current use it is an adjective and verb meaning "shaking or trembling in voice, often due to nervousness or emotion". That sense is explained by the older material without requiring a speculative semantic step: the inherited or borrowed base supplies the field of meaning, while the English formation fixes its modern role. The -ing ending supplies a participial or action-noun shape. The surface form is compositional: its joined elements remain visible in the modern word. The word's history is thus visible in its construction: the components remain interpretable even after the whole expression has settled into a conventional English meaning.