No official guess because 100% Google's effort, but there's also a real Henry Sherman in the assassination saga:
"Henry Sherman was a personal friend of President Abraham Lincoln, who on the morning before his assassination in 1865 tendered him the Chief Justiceship of the Territory of New Mexico; his commission was afterwards sent him by President Andrew Johnson, but he resigned the office very soon." https://en.m.wikipedia.org/wiki/Henry_Sherman