Username is one of the most basic parts of both offline and online applications in today’s digital world and is used for many purposes such as logging, authentication, and account creation. It is an established practice to obligatorily take a username when creating an account in Online Social Network (OSN) applications as well. However, a username can include various information about its user even though it is often restricted to be a short string. In this study, an analysis is conducted on usernames of Turkish users of Facebook which is a popular OSN application. The results obtained by using a lexicon-based approach showed that it is possible to correctly detect the first names from usernames with a percent of up to 69.23. On the other hand, the success of gender identification based on detected first names has also reached up to a percent of 86.20.