Watch the Pickin' On Chet online guitar lesson by Pete Huttlinger from 50 Fingerpicking Licks You MUST Know
I got this from a guy who said he got it personally from Chet Atkins. This is a lick with many applications. You can do this over a variety of chords including G, Cmaj7, Em, Em7, Am9 just to name a few. BTW - When I moved to Nashville 29 years ago, Chet Atkins was the very first person I spoke to not more than 30 seconds after arriving. Talk about a good sign.