Dick Talleur calls this nymph the Pea-Ca-Bou Brown, and I can only find mention of this pattern in Hooked on Fly Tying - Classic Wet Flies & Nymphs, Bennett-Watt Entertainment, Inc. (https://amzn.to/2Mp1yFU)
It's a tremendous all-a-round nymph that uses two of the best materials out there Peacock herl and marabou. I've found smaller sizes are effective little black stone flies, and larger versions imitate Isonychia, also known as the Slate Drake.
It's simple, and once you get used to handling the marabou, a fast pattern to tie.
I think everyone knows the Pheasant Tail Nymph, but I'm not sure how many know Sawyer's Pheasant tail nymph. The pattern is dead simple, and like most patterns I tie, it follows the K.I.S.S. rule.
For those who don't know the pattern, it's a killer. Frank Sawyers designed it to "Baetis" nymph, or "olives." I've found it's also a good imitation of the "Ephemerella" nymphs, including the Hendricksons and Sulphurs nymphs. For the "Baetis," tie the nymph in sizes 16 - 20, and for the "Ephemerella," tie it in 14 - 16. If you have a long Pheasant tail, then a size 12 is possible.