In woodworking, a kerf is the notch or groove made my a cutting tool.
“Off the kerf” is a play on the phrase “off the cuff”.
One of my several hobbies is woodworking. There isn’t much depth about “off the kerf”. It’s simply a name I came up when I was trying to get a domain name for a woodworking website. I liked the name so I decided to use it for this site. This site won’t be just for showcasing my woodworking. There will likely be some of that, but I’m not going to limit myself to just that.