First penned in the 18th century by David Garrick as part of a 1759 opera called "Harlequin's Invasion", it was set to music by Dr Boyce of Kensington.
Source: (Royal navy fact sheet!)
The melody appears in the Gillespie Manuscript of Perth, 1768.
Chappell's Popular Music of the Olden Time vol. 2 1859 reports that James Boswell, biographer to one Dr. Johnson reportedly sang the song while visiting Corsica: "Never did I see men so delighted with a song as the Corsicans were with 'Hearts of Oak'. 'Cuore di querco' cried they, 'bravo Inglese'. It was quite a joyous riot. I fancied myself to be a recruiting sea-officer—I fancied all my chorus of Corsicans aboard the British fleet."
These lyrics are based on the version performed by the Longest Johns in their Youtube Video.
Come, cheer up, me lads, 'tis to glory we steer,
To add something more to this wonderful year;
To honour we call you, as freemen not slaves,
For who are so free as the sons of the waves?
Heart of Oak are our ships, jolly Tars are our men,
We always are ready: Steady, boys, Steady!
We'll fight and we'll conquer again and again.
We ne'er see our foes but we wish them to stay,
They never see us but they wish us away;
If they run, why, we chase them, and run them ashore,
For if they won't fight us, what can we do more?
They say they'll invade us, our terrible foes,
They'll frighten our women, our children, our beaus
But should their flat bottoms in darkness set oar,
Still Britons they'll find to receive them on shore
We still make them feel, and we still make them flee
and drub them ashore as we drub them at sea,
So come cheer up me lads, with one voice let us sing,
Our soldiers, our sailors, our statesmen, and king