Jack tar
What's the meaning of the phrase 'Jack tar'?
'Jack tar' is a generic name for a seaman of the British Royal Navy.
The term was most commonly use during the period of predominance of the British Empire, when 'Britannia ruled the waves'. It was usually applied to sailors below the rank of officer.
What's the origin of the phrase 'Jack tar'?

...his Grace and my Lady Dutchess, Jack Tar, and Mrs. Top-gallant-Sail, with every Coffee-Man, and his Wife.
The derivation of 'Jack tar' seems fairly straightforward. Firstly, let's look at 'Jack'.
In England, since the 14th century, 'Jack' has been a synonym for 'the common man', as is 'Jock' in Scotland. An early example is found in John Gower's Middle English poem Confessio Amantis, 1390:
Therwhile he hath his fulle packe,
They seie, 'A good felawe is Jacke'.
Whenever a name was needed for any stereotypical common fellow, Jack was chosen. Examples of this are:
Jack of all trades
Jack the giant killer
Jack in the box
Jack Robinson
Jack the lad
and so on...
A sailor was the common man at sea. Jack took the 'common man' part. 'Tar' was chosen to refer to all things sailor-like.

Tar was used as waterproofing on many parts of the ship - between the planking of the hull and deck, on ropes and on sheeting. Sailors hands, hair and clothes would become smeared with tar. They used tar to braid their pigtails and to waterproof their canvas hats and trousers. No wonder really that a sailor would be called 'tar' - the perfume of it would have been unmissable.
The extended form 'Jolly Jack tar' began to be used from around the turn of the 19th century. Here's an early example from The Edinburgh Advertiser, April 1802:
Two jolly Jack tars exhibited a complaint at Bow-street on Saturday evening of having severally been robbed.
This doesn't seem to be because sailors were thought to be especially jovial. Jolly, or jollie, was the name given to a royal marine. This is recorded in Admiral W. H. Smyth's The Sailor's Word-Book: an alphabetical digest of nautical terms, 1867:
Tame jolly, a militiaman: royal jolly, a marine.
The above book is an invaluable and exhaustive list of the words used by sailors in the 19th century.
It seems that sailors weren't especially fond of the name Jack tar as, although 'Jack' is mentioned in the book in many contexts, 'Jack tar' doesn't appear. What is there is what sailors preferred to call themselves - 'Jack afloat'.
See also: 'Jack' phrases.
