Die hard disappear or change very slowly; the expression seems to have been used first in the 18th century of criminals who died resisting to the last on the Tyburn gallows in London. At the battle of Albuera in 1811 during the Peninsular War, the commander of the British 57th Regiment of Foot exhorted his men to ‘die hard’; as a result of their heroism, the Regiment was nicknamed the Die-hards. The term was later applied to political groups particularly resistant to change.
die in harness die before retirement.
you can only die once used to encourage someone in a dangerous or difficult enterprise; recorded from the mid 15th century.
See also eat, drink, and be merry, for tomorrow we die, whom the gods love die young, the good die young, young men may die.