A "firstnamer" (n.) is one who refers to an unknown, non-present party using only their first name whilst fully aware that those with whom he is presently speaking have no friggen idea who the other person is.
"Firstnaming" (v) is achieved by intentionally omitting key descriptors that generally precede an unknown person's name, such as, "my friend" or "this girl I work with". Such descriptors are a courteous way to avoid alienating the present party by acknowledging their lack of familiarity with the unknown person.
"Firstnaming" is occasionally committed by mistake, but more often is used as a conversational trick to create the illusion of great social reach and likability. This is generally the result of a strong desire for acceptance.
The act of "firstnaming" is frowned upon in many cultures for 1) adding layers of useless information, tension and complexity to an otherwise normal conversation, 2) being a cheesy way to invite discussion, 3) displaying a lack of security in the strength of one's personal relationships at the expense of other peoples time and energy.
"...and then Steve was all like, dude you are the man for chugging that beer, and I was like, Yeah Steve you're so crazy man. Steve is so weird sometimes, you know?"
"I don't have any friends named Steve and don't know who the fuck you are talking about, man."
"Oh. Well, Steve's a buddy from work. You don't know him I guess."
"Yeah, you guessed right you fucking firstnamer. Get the fuck out of my face."