Origin: Welsh, Old Norse
Meaning: I've seen two possible origins for this name. The first is that it comes from Welsh kaleto meaning "hard, violent" and dwfr meaning "water, stream" so essentially meaning "rocky water" or "violent water".
It could also be derived from Old Norse kalfr meaning "calf" and dalr meaning "valley" essentially meaning "calf valley".
Calder is a surname that derived from a habitional place name as well as the name of several rivers in Scotland, England, and Australia.