Both English. Heald is from the Old English Hylde, meaning a slope or hillside. So the name tells us that the original bearer lived near such a topographical feature. Hildreth and Hildred are Northern English names. I suspect (don't know in other words) that they derive from a Germanic given name from the words HILD, meaning "battle", as in Hildebrand, and RED, meaning "counsel", as in Aldred.