The boat in Sammy's Bar is as I recall in Malta - Valletta Harbour? So the possibly Maltese word is not too likely to turn up in ?early 19thC England. (By the way, are you sure it's a boat? I've a vague memory of some other harbour activity being intended, and I've even heard a singer explain it has something to do with dice being thrown! Cyril Tawney wrote the song, there will be a full explanation in one of his songbooks.) From the context the much more likely explanation is a local technical word for a bale, or for the rope or net that is put round such a bale. Nothing helpful in my big English Dictionary, however. Very speculatively, something to do with the die shape of a bale, or else some covering to protect the dye colouring? All things are possible.