The fathom, a unit of length in the imperial and U.S. customary systems, equals six feet (1.8288 meters) and historically measured water depth, reflecting its maritime origins. While primarily a practical measure, it also appears metaphorically in literature.
Shakespeare evokes it in The Tempest to poeticize submerged depths, while Poe uses it to describe unfathomable whirlpools, blending physical and existential mystery. Emerson contrasts superficiality with "million fathoms deep," highlighting its symbolic resonance. Though largely replaced by metric units, the fathom endures in nautical traditions and literary imagination, bridging empirical measurement and the unknowable.