A gnat smoke is an old-fashioned insect repellent. To make a gnat smoke one simply takes an old t-shirt or any other unused rag, light it on fire, then drop it into an empty metal can or bucket. The rag will smolder for hours, emitting a small flume of smoke that will prevent you from being eaten alive by mosquitoes and, yes gnats, on summer evenings when you  are enjoying an outdoor gathering.
It was a staple of many yards where I grew up in rural Alabama. It is a testament to ingenuity and remains today as a pleasant memory from my childhood.
It is uniquely southern, but would work just as well anywhere; It is crude, but effective; It's simple, but somehow it just works; just like us. That is why we chose it for our name.