Loquaciousness is the quality of being very chatty or talkative. Your friend's loquaciousness is much more charming during a dinner party than first thing in the morning, when you're still half asleep.
If people comment on your loquaciousness, it means they think you talk a lot. Loquaciousness comes in handy when you're making small talk at a party or filling air time on your local radio talk show. If you have the quality of loquaciousness, you're loquacious, which comes from the Latin loquax, or "talkative," ultimately from the root word loqui, "to speak."