It's been suggested that many of these names are 'American'.
Some of them indeed are American in style. But they are very, very dated.
These days, Americans are giving both boys and girls surnamey names.
I know girls named Bennett, Campbell, Cameron, Bellamy, Merrick, Merritt, Aniston, Arden, Callahan, Collins, Linden, Madigan, Havilland, Holliday, Hollis, Kennedy, Cassidy, Reese, Sheridan.