An Etymological Dictionary of the German Language/Annotated/Faden
Faden, masculine, ‘thread, file, shred,’ from the equivalent Middle High German vaden, vadem, Old High German fadam, fadum, masculine; Gothic *faþms is wanting. Compare Old Saxon fathmos, ‘both arms stretched out,’ Anglo-Saxon fœþm, ‘both arms distended, embrace, protection, bosom,’ English fathom (a measure), Old Icelandic faðmr, ‘both arms, bosom.’ Consequently the primary sense is ‘encompassing with both arms,’ which could be adopted as a measure (see Klafter); hence the use of ‘fathom’ as a measure in English, Scandinavian, Low German, Dutch, and also in Modern High German (adopted from Low German and Dutch). The Modern High German meaning ‘thread’ is a recent development; its literal sense is ‘as much yarn as can be measured with the arms stretched out.’ The primary sense, ‘encompassing,’ results from Gothic faþa, feminine, Middle High German vade, feminine, ‘hedge, enclosure.’ The base of the cognates is a Teutonic root, feþ, faþ, pre-Teutonic pet, pot, which accords with the Greek πετ in πετάννυμι, ‘to spread out,’ πέταλος, ‘outspread, broad, flat’; Latin patere, ‘to stand open,’ is even more remote.