Wellspring comes from Middle English welle spryng, a compound of well ('a spring of water') and spring ('a source, place of rising'), both from Old English (wella and spring). In current use it is a noun meaning "a source of continual supply, especially of something abstract". 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 surface form is compositional: its joined elements remain visible in the modern word. The historical chain includes Old English wella and Old English spring. Related English forms include well and spring. 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.