Merman was a tiny woman with a fog horn voice Ethel changed her last name from Zimmermann to Merman without thinking that some people might think she was Jewish. That is why Ethel often told everyone she was a happy Episcopalian.
She thought Zimmermann was too long for theater lights.
Ethel Merman was a great theater star, who wasn't particularly smart or sophisticated.
Yet "Annie Get Your Gun" and "Gypsy" were specifically written for Merman..