Actually, someone told me that George Antonius used the term "nakba" in his Arab Awakening [published 1938] referring to the mandate for the Jewish National Home in the early 1920s. Be that as it may, an Arab intellectual, an Arab Christian, Constantine Zurayk, used the term, as did other Arabs, after the Israeli War of Independence, to refer to the Arab defeat at the hands of the lowly, despised Jews. It was not then used for the suffering of the Arab refugees. Here Barry Rubin quotes from Zurayk:

Constantine Zurayk was vice-president of the American University of Beirut. His book was entitled The Meaning of the Disaster. Here’s the key passage:
“Seven Arab states declare war on Zionism in Palestine, stop impotent before it and turn on their heels. The representatives of the Arabs deliver fiery speeches in the highest government forums, warning what the Arab states and peoples will do if this or that decision be enacted. Declarations fall like bombs from the mouths of officials at the meetings of the Arab League, but when action becomes necessary, the fire is still and quiet, and steel and iron are rusted and twisted, quick to bend and disintegrate.”
This is the old style of Arab discourse. Zurayk openly acknowledged the Arab states rejected all compromise, made ferocious threats, and invaded the new state of Israel to destroy it. For him, the “nakba” taught that they needed to modernize and democratize their system. Only thoroughgoing reform could fix the shortcomings of the Arabic-speaking world.

So today's talk of  "disaster" [nakba] was not originally a humanitarian expression but an admisstion of shameful defeat.