I find most people have auditory processing difficulties when it comes to names. Whenever someone says a name, no matter how familiar the person mentioned is, the response is often "who?" I, for one, actually hear names first time and hardly ever need to ask them to repeat the name.
Sometimes people ask who? at a simple name that's easy to hear. Like if someone has a girlfriend and someone asked what her name was and he said "Rebecca", a simple, common name that doesn't really sound like any other name, and they still go "who??"
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Female