"El Pueblo de Nuestra Señora la Reina de los Ángeles del Río de Porciúncula" (Yes, that's the original.) I've lived here almost half my life and I did not know. I never took the time to investigate until now.
In 1769, a Franciscan friar who was exploring California named a river "Nuestra Señora de los Ángeles de la Porciúncula".  In English it means "Our Lady of the Angels of Porciúncula".  That was just the name of the river.
Now for the city.  As a settlement was established, along the banks of this river with the long name, it came to be known as (brace yourself) "El Pueblo de Nuestra Señora la Reina de los Ángeles del Río de Porciúncula", or "The Town of Our Lady the Queen of Angels of the Porciúncula River".  A very small town with a very long name!  And, in the naming of the town, the Virgin Mary went from "Our Lady of the Angels" to "Queen of Angels".
Here is the cool historical part. Porciúncula is the most sacred place of the Franciscan Order of the Roman Catholic Church. Actually, it is still a small church in Italy which is now located inside of a larger church called the Basilica of Santa Maria degli Angeli. The basilica is located near Assisi, Italy in Umbria (central Italy) and it is the place where the Franciscan movement originated. "Porciúncula" actually means "small portion of land" and the humble church, of the same name, is where St. Francis of Assisi died.
Needless to say, this lengthy and descriptive name for our city was obviously, and officially, shortened to just "Los Angeles". Sometimes I wonder why certain words remained over time and others just dropped away. Why did they not retain "our lady" (Nuestra Señora) or "our queen" (Nuestra Reina) to whom the angels actually belong?  I imagine "Porciúncula" was jettisoned early on (sorry Saint Francis). I can't even fake pronounce it in my head.
In spite of the reduced word count, our city name remains in Spanish and it means "The Angels".  As you know, we don't even say "Los Angeles" very much anymore. We just say "L.A.".  Maybe in the future it will morph again into a short grunt or quick hand gesture to save time. In any case, now we know the origins. I feel better.