As you can see, your first name is shown in this article(only when you are logged in). The plugin MDGetuserfield can show a field from the user database. Download the file and install it as a Joomla! plugin. Under parameters the field to be shown can be selected. The name is shown by default.
Place mdgetuserfield in sprockeds in your content, the specified field will be shown.
This plugin is a simplified version of Getcbfield