Davis usually means "son of David," with the Welsh form Dafydd standing behind many British Isles lines. In Wales the older style was ap Dafydd—"Dafydd's son"—which settled into Davis and the cousin spelling Davies as fixed surnames.
Wikipedia also notes a minority story that some early forms corrupt Dyfed, an old regional name. That is why this page stays at likely rather than high: the everyday family meaning is still the David patronymic, but origin stories are not identical for every line. Either way, it is a parent's-name surname, not a trade or a hillside.