I don't have a problem with this as a first name. It doesn't sound like a surname to me like Johnson or Jackson. Rather, it reminds me of other male first names like Billy or Bobby. But Murphy gives the impression of an old man in my opinion. It doesn't sound like a female name. If you want a similar sounding female name, how about Miranda or Sophie or Phoebe or Melanie or Stephanie?
My name is Murphy and I am also a woman. I feel like many people think that the name isn't good; especially for a girl. However, I feel that it fits my personality extremely well, and when I tell people my name they usually like it. Concerning nicknames, I agree that there aren't many other than Murph, or even Mo. But I love that my name is unique and that it is something that I can't picture myself being called anything else.
It's only splendid as a surname yet awful as first name. Plus the Cillian Murphy association is too heavy. He's an incredibly good actor with a nice personality but it'd be annoying to repeatedly deal with jokes or comparisons, specially at school time.
Murphy sounds so harsh as a given name. I don't like it even on a boy and I do like masculine names! It's just too rough and coarse. It would be okay on a cat or a dog, though.
I hate this name for both sexes. I can't really imagine it on a guy, and on a woman, it sounds very ugly. It actually sounds like the name of a shabby middle-aged woman with a hideous 80s-like hairstyle with hair that looks electrified and ugly, loose-fitting clothes.