Definition of "Charmian"

Help me away, dear Charmian, I shall fall:

c. 1606–1607, William Shakespeare, “The Tragedie of Anthonie and Cleopatra”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene iii]

Charmian Lyle had given herself her first name at the age of sixteen, upon encountering it in an English novel. Her baptismal name was Ethel. When her husband Walter was extremely angry with her, he called her Ethel. Charmian, she thought, suited her much better. She didn't think she looked, felt, or sounded like Ethel. Nor like her middle name, which she really detested, Edna.

1979, Mary McMullen, But Nellie Was So Nice, Doubleday, page 23