According to the credits, this season is based the book, "People of Darkness", by Tony Hillerman, published 1980. This follows the previous, "Listening Woman", 1978, books three and four of Mr. Hillerman's series, upon which season 1 was loosely based.
Na'nilkaadii , the episode title, is Navajo for shepherd or sheep herder.
Based on the newscast overheard by Emma in the Hospital, the year is 1971, and the National Draft Lottery drawing was being conducted from the Selective Service headquarters in Washington DC. That puts the story in the era of the Vietnam Conflict, when the United States sent troops over to Vietnam to stem the spread of Soviet Communist ( The Soviet Union is now known as the Russian Federation). The draft lottery was a way to muster young men to serve in said conflict.
A Martinez, aka Sheriff Gordo Sena and Zahn McClarnon, aka Joe Leaphorn both starred in Longmire from 2012-2017.
The timeline for the Novel on which it is based on, "People of Darkness" is about thirty years. The actual adaptation occurs over nine days.