I'm quite prepared to accept that 'doldrums' might have a euphemistic implication, but in order for it to be a euphemism it would still need an alternative primary meaning, otherwise it would just be slang (rather bizarre slang at that) .

Thinly veiled euphemism is a common feature of folk song ('long peggin awl' etc) but direct sexual slang is much more uncommon is it not? Only example of sexual slang that springs to mind is 'quim' in Firelock Stile. (There's also the Bastard King of England but that's not really a folk song.)

So 'doldrums' as slang for 'tattered rags from a coat or trousers' is not incompatable with the euphemistic reading, in fact it makes a lot of sense. Dreadlocks is more incompatable, which perhaps makes it a less likely meaning given the clear use of euphemism in the 'small furrow' verse.

Really annoying that there don't seem to be any other slang or euphemistic uses of 'doldrums' anywhere else. You'd think it might crop up in Irish literature somewhere.

jon