英语词源字典 - 在线词源网站

board (n.2)[board 词源字典]: "side of ship," Old English bord "border, rim, ship's side," from Proto-Germanic *bordaz (cognates: Old Saxon bord, Dutch boord, German Bord, Old High German bart, Old Norse barð), perhaps from the same source as board (n.1), but not all sources accept this. Connected to border; see also starboard.

If not etymologically related to board (n.1), the two forms represented in English by these words were nonetheless confused at an early date in most Germanic languages, a situation made worse in English because this Germanic root also was adopted as Medieval Latin bordus (source of Italian and Spanish bordo). It also entered Old French as bort "beam, board, plank; side of a ship" (12c., Modern French bord), either from Medieval Latin or Frankish, and from thence it came over with the Normans to mingle with its native cousins. By now the senses are inextricably tangled. Some etymology dictionaries treat them as having been the same word all along.[board etymology, board origin, 英语词源]
inextricable (adj.): early 15c., from Latin inextricabilis "that cannot be disentangled," from in- "not, opposite of" (see in- (1)) + extricare (see extricate). Related: Inextricably.