Words by David Garrick (not Dibdin though it seems like it ought to be).

The original chorus seems to be:

Heart of oak are our ships, heart of oak are our men;
We always are ready, steady, boys, steady!
We'll fight and we'll conquer again and again.

Now when I was much younger I learned this as "Heart of oak are our ships, Jolly tars are our men..." etc.

Does anyone know when or how this alteration was made?