It has long been said that the best sort of furniture polish is 'elbow-grease', that is, there is no substitute for hard rubbing to create a lustrous shine. The term itself is older than might be imagined and dates back to at least the 17th century when it was used in print by the English metaphysical poet Andrew Marvell in Rehearsal Transpros'd, 1672:
Two or three brawny Fellows in a Corner, with meer Ink and Elbow-grease, do more Harm than an Hundred systematical Divines with their sweaty Preaching.
Marvell was suggesting that, although religious meetings could be disrupted or broken up by the speakers' opponents, printed material could be circulated unhindered. Of course, Marvell was alluding to writing when he used the figurative expression 'elbow-grease'. It was also used later in the same century, as it is used now, just to mean sweat or effort. An example of that usage is found in the 1699 New Dictionary of the Canting Crew:
Elbow-grease, a derisory Term for Sweat.
The expression's inclusion in that dictionary, which itemises the language of the streets, suggests that it was a lower-class term.
Other countries have expression that are near-enough identical. In French we have 'huile de bras' or 'l'huile de coude', which translate as 'elbow-grease' and in Danish we find 'knofedt', which translates as 'knuckle fat'.