Meaning
This means to do your work with complete determination and commitment.
Origin
In 1400 this line was printed in Turnament Totenham:
“Ther was gryndulstones in gravy, And mylstones in mawmany.”
The first known citation came in year 1532 in John Frith’s A mirrour or glasse to know thyselfe:
“This Text holdeth their noses so hard to the grindstone, that it clean disfigureth their faces.”
Meaning
This phrase is used to say that we should do optimal use of resources and save them until they are absolutely needed.
Origin
In 1856, Edward Hayes wrote it in Ballads of Ireland:
“There is a well-authenticated anecdote of Cromwell. On a certain occasion, when his troops were about crossing a river to attack the enemy, he concluded an address, couched in the usual fanatic terms in use among them, with these words – ‘put your trust in God; but mind to keep your powder dry’.”