Mahatma Gandhi was a pacifist and anti-violence leader. Why did he adopt the slogan "Do or Die" for the Quit India movement? It sounds more like a strong, desperate phrase.
Non-violent resistance doesn't mean there won't be violence (including possibly death) happening. It just means you won't be the one committing it. In fact, it is the goal to induce the oppressor to respond with violence, to draw everyone's attention to the fact that they have no authority over the situation other than brute force.
As an example, I give you the Dharasana Salt March, which I can't describe any better than today's Wikipedia entry on it:
...the march continued under the leadership of Sarojini Naidu, a woman poet and freedom fighter, who warned the satyagrahis, "You must not use any violence under any circumstances. You will be beaten, but you must not resist: you must not even raise a hand to ward off blows." Soldiers began clubbing the satyagrahis with steel tipped lathis in an incident that attracted international attention. United Press correspondent Webb Miller reported that:
Not one of the marchers even raised an arm to fend off the blows. They went down like ten-pins. From where I stood I heard the sickening whacks of the clubs on unprotected skulls. The waiting crowd of watchers groaned and sucked in their breaths in sympathetic pain at every blow. Those struck down fell sprawling, unconscious or writhing in pain with fractured skulls or broken shoulders. In two or three minutes the ground was quilted with bodies. Great patches of blood widened on their white clothes. The survivors without breaking ranks silently and doggedly marched on until struck down....Finally the police became enraged by the non-resistance....They commenced savagely kicking the seated men in the abdomen and testicles. The injured men writhed and squealed in agony, which seemed to inflame the fury of the police....The police then began dragging the sitting men by the arms or feet, sometimes for a hundred yards, and throwing them into ditches.
Vithalbhai Patel, former Speaker of the Assembly, watched the beatings and remarked, "All hope of reconciling India with the British Empire is lost forever." Miller's first attempts at telegraphing the story to his publisher in England were censored by the British telegraph operators in India. Only after threatening to expose British censorship was his story allowed to pass. The story appeared in 1,350 newspapers throughout the world and was read into the official record of the United States Senate by Senator John J. Blaine.
This youtube clip contains a dramatization of this from the 1981 Ghandi biopic that is worth seeing (although it is far too antiseptic).
That is what is meant by "do or die". Walking willingly into harm's way rather than submit.
'Do or Die' is a very common phrase in India which almost never infer violence. Google interpret this phrase as 'persist, even if death is the result.'
Thus, what Gandhi was trying to convey millions of Indians, were to strive for complete independence, even if death is the result. It doesn't convey violent message but very basic desperation, which was the need of the hour.
It was not a desperate phrase by any means. Since the 1920's, Indians were protesting against the British for freedom. But the British showed no signs of relenting. India was the brightest jewel in the British Crown and there was no way that the British would relinquish their hold on it.
Finally, Gandhi had enough. He knew that there had to be a decisive push for freedom and no more pussyfooting this time. It was to be the ultimate showdown, with no compromise on the final objective: Independence for India and the complete ejection of the British Raj. Even if this meant total civil disobedience and death at the hands of the British.
Hence this phrase was coined. This was to tell the British that there was to be no negotiation or no compromise on the goal for Purna Swaraj (Complete and unconditional independence).
That Gandhi was an ethical pacifist is largely a romantic conceit. He was in fact a pragmatic pacifist. He knew that it would be relatively difficult to rouse the Indian people to overthrow the British with violence, and thus promoted pacifism as the best way to accomplish that goal.