Bad language coming from the boathouse (4)

I believe the answer is:

oath

'bad language' is the definition.
(I've seen this before)

'coming from the boathouse' is the wordplay.
'coming from' indicates the answer is hidden within the clue.
'OATH' is hidden within 'boathouse'.

(Other definitions for oath that I've seen before include "A curse - or a pledge" , "Curse - sworn statement" , "A curse or a vow" , "Solemn promise to tell the truth or be loyal" , "Imprecation" .)

I've seen this clue in The Irish Independent.

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