Was it Balanchine who first used the title "choreographer" to refer to his work? If so, where did I read that?

I don't think he was the first to call himself "choreographer", but he insisted upon being billed this way for his work on Broadway.

I'm fairly sure this was in Taper, and it has been picked up by other biographers and writers as well.

Before that, the term was customarily "dance director", or other similar formation.

Balanchine was the first to insist on getting credit in his broadway word for 'choreography' but he seems to have disliked the word 'choreographer.'
he preferred "balletmaster" - as his tombstone, like Petipa's. attests.
it's said, i believe, that he was the first, or among the first, to get choreography credit for his show (and maybe movie) work.
most russian lists of credits for ballets before and during Balanchine's day in russia also use the word 'balletmaster,' not 'choreographer.'

Didn't Lifar, in the mid-30s, use "choreautor" or something like that?