Kim, the protagonist, isn't actually crowned the title; Gigi Van Tranh, a minor character, is. For a while I thought it might be a play on the word "miss," which can also mean to feel the loss of something/someone. Saigon was renamed Ho Chi Minh City upon the end of the war, so "Miss Saigon," I figured, was meant to be a longing for the time before the Communists took over. Kind of like
Gone with the Wind is a reference to the dissolution of the antebellum South. I don't know.
Anyone?
Salve, Regina, Mater misericordiae
Vita, dulcedo, et spes nostra
Salve, Salve Regina
Ad te clamamus exsules filii Eva
Ad te suspiramus, gementes et flentes
O clemens O pia