Campbell is Scottish Gaelic cam + beul: "crooked mouth" or "wry mouth," originally a nickname. Clan Campbell later became one of the great Highland families, but the surname's literal start is that facial byname—not a romantic landscape.
Medieval clerks sometimes Latinized it as de bello campo ("of the fair field"), a folk etymology that also nudged some translations toward Beauchamp. Irish Mac Cathmhaoil lines were sometimes rendered Campbell too. Lead meaning for Scottish Campbells remains crooked mouth. Families carried the name across the Atlantic without changing its core sense.