Randy Dandy, Oh
This is a sea shanty dating back to the 18th or 19th century, likely American in origin. Sea shanties were sung by sailors as a means of coordinating labor with a consistent rhythm. These songs frequently feature a single leading voice who calls out a line or two before the other sailors respond in chorus with one or two repeating lines. The content of shanties was drawn from the common experience and lifestyle of sailors. This particular shanty contains references to a common voyage made around the southern tip of South America through some of the most treacherous waters navigated by mankind.

Verse 1

Now we are ready to head for the Horn,
The Horn is a common sailing reference to Cape Horn, at the southern tip of South America.

Way, ay, roll an' go!
A reference to the rolling motion of a ship on rough ocean waters. Given the lack of landmasses to act as wind breaks, masses of air displaced from the equator, and the Earth's rotation, the southern 40, 50, and 60 degree latitudes experience extremely powerful west-to-east winds. Seas there are known by their latitudes as the Roaring Forties, Furious Fifties, and Shrieking Sixties. This is one of the repeated chorus lines, so it will not appear further in the analysis.

Our boots an' our clothes boys are all in the pawn,
This line could either be a reference to the sailors having securely stored their extra gear below deck before readying for the rough voyage, or a reference to the hopelessness of challenging the Horn and having sold everything including boots and clothes. Pawn either refers to having sold things off, or is an antiquated use of the word, referring to storing gear on shelves.

To be rollickin' randy dandy O!
Again, a reference to the rolling motion of a ship. Rollickin' is an antiquated term for rolling. It's current use is more figurative to connote a situation about to lose control. This is the other recurring chorus line; its analysis will not appear further.

Verse 2

Heave a pawl, oh, heave away,
A pawl is a lever connected to a system of gears. This type of crank was commonly seen on ships as a means of raising and lowering anchors.

The anchor's on board an' the cable's all stored,
Describes the process of heading out to sea by retracting the anchor.

Verse 3

Man the stout caps'n an' heave with a will,
A capstan is a device used to haul ropes with multiple men rotating vertical-axled wheel.

Soon we'll be drivin' her 'way up the hill,
Cape Horn, the Strait of Magellan, and Drake's Passage are notorious for rogue waves up to 98 feet tall. Average swells are between 12 and 30 feet.

Verse 4

Repeats Verse 2

Verse 5

Heave away, bullies, ye parish-rigged bums,
Parish-rigged refers to a ship in poor condition due to neglect by the owner (torn sails, worn rope, etc). This is likely a reference to the sailors and their deliberate self-neglect for hygiene and safety. Sailors were historically known as rough, transient people without a proper home and exhibited hardened exteriors.

Take yer hands from yer pockets and don't suck yer thumbs.
A call to action and courage. Facing these extremes was not for the faint of heart.

Verse 6

Repeats Verse 2

Verse 7

We're outward bound for Vallipo Bay,
Vallipo Bay is english slang for the Chilean port city of Valparaíso. Reaching this point having sailed east-to-west signified that a ship had left behind the danger of Cape Horn and could expect to enjoy the calmer waters of the American West Coast.

Get crackin', m' lads, 'it's a hell of' a way!
Another reference to the difficulty of the Cape Horn crossing.

Verse 8

Repeats Verse 2

Verse 9

Repeats and slows down Verse 2 to conclude the shanty.

Sources

Origin of the Randy Dandy, Oh and Expanded Lyrics
http://brethrencoast.com/shanty/Randy_Dandy.html

Sea Shanty Construction and Purposes
https://en.wikipedia.org/wiki/Sea_shanty

Cape Horn
https://en.wikipedia.org/wiki/Cape_Horn

Wind in the extreme south of the Southern Hemisphere
https://en.wikipedia.org/wiki/Roaring_Forties

Pawn as shelves
https://books.google.com/books?id=1NjWAAAAMAAJ&pg=PA218&lpg=PA218&dq=pawn+sailing+slang&source=bl&ots=tI_fNP4QW4&sig=kbM9Qrl-DaiexzXMXtIYFyVvbuI&hl=en&sa=X&ved=0ahUKEwjBve66qo3aAhUO1GMKHZxaCBIQ6AEIVzAE#v=onepage&q=pawn%20sailing%20slang&f=false

Pawl Definition
https://en.wikipedia.org/wiki/Winch

Capstan Definition
https://en.wikipedia.org/wiki/Capstan_(nautical)

Parish-rigged Bums Definition
http://www.oxfordreference.com/view/10.1093/oi/authority.20110803100306560

Valipo Bay Reference
https://en.wikipedia.org/wiki/Valpara%C3%ADso