Fathom
Length · Also called: fadm
That is
1.829 m
1 fathom (imperial)
The other way round: 1 km is 546.8066 fathoms.
- Period: medieval to today
- Region: the UK
- Goods: soundings, rope, timber, mine shafts
What the unit was used for
The fathom is six feet and the clearest surviving body measure in English: Old English fæðm meant the outstretched arms or an embrace.
Cognates confirm the sense, Old Norse faðmr for embrace and Old Saxon fathmos for the outstretched arms.
The practical link is direct, because a seaman hauling a sounding line hand over hand with his arms spread counts one fathom per pull.
British Admiralty charts gave depths in fathoms until the change to metric charts began in the 1960s, and the same span governed rope, cable, timber and the depth of mine shafts.
To fathom something is the same word: it is sounding the depth of water.
In the system
1 fathom = 6 feet = 2 yards; about 100 fathoms to a cable