I have always known "Do your balls hang low?' to the tune that also carries 'In the South of France, Where they do the hula prance, He'll sing "Nelly put your belly close to mine"', as well as to the Jacky Tar hornpipe: ~~ a mock oriental tune which I can't at the moment precisely place; is it perhaps from Samson & Delilah? Can anyone identify the tune I mean?

W H Logan's The Pedlar's Pack Of Ballads & Songs [Edinburgh 1869] also contains Jack Robinson; & also, which no-one above has mentioned, a song called JACKY TAR which has the refrain "With his trousers on";
of which Logan notes "The air to which it has been sung is the well-known dance tune known as the Sailor's Hornpipe, which, it is believed, was danced long before the tune was rendered vocal". Jack-ashore courts a girl successfully, with, it is stressed at the end of each verse, 'his trousers on' ~~ presumably with ref to the fact that, as Phillis Cunnington & Catherine Lucas note in 'Occupational costume in England from the 11th century to 1914' {A&C Black 1967}: "Trousers. or trowsers were not commonly worn in the 18C. Their use was restricted to labourers, sailors, and soldiers, and on occasion to the country squire."

~Michael~