Keep Calm and Carry On!

We used to have this bright red poster with white writing on it that said, "Keep Calm and Carry On". Originally created in 1939 at the start of World War 2 by the British Government to boost morale and raise people's spirits in the light of huge global uncertainty, these words became a symbol of the determination and hope held by our country.
Calm is an interesting word and comes from the French word calme which means "tranquillity, quiet" and the Italian word calma translating as "quiet, fair weather". In the 15th century it changed to mean a more figurative "freedom from agitation or passion". Looking at these, the foundations of the word communicate calm as being still, knowing stillness.