the.com/stream bed

means The channel of ground, rock, or sediment that a stream flows over and periodically reshapes.

from A straightforward compound: 'stream' tracing back to Old English 'strēam' (flowing water, related to Old Norse 'straumr' and a wider Germanic family of words for 'flow'), joined to 'bed' in its old sense of 'bottom surface or resting place'—the same 'bed' as in riverbed, seabed, or a bed of flowers. No hidden story here; the word simply does what it says, laying the water down in its place.