Bit·ter n. Naut. AA turn of the cable which is round the bitts.
Bitter end, that part of a cable which is abaft the bitts, and so within board, when the ship rides at anchor.
bitter end
n 1: the final extremity (however unpleasant it may be); "he was
determined to fight to the bitter end"
2: (nautical) the inboard end of a line or cable especially the
end that is wound around a bitt