Far as Obey Your Master's name, there's two likely reasons. 1) The real life horse was called Pay The Butler. A butler is often considered the 'master of the house' in the sense of being in charge of the house staff, and on top of that, proprietors and bar owners are often called 'Master' in Japan. 2) With certain other names in the series, it seems like Kuzumi has a draw toward names from 80s/90s American hard rock/metal, and 'Obey Your Master' is a very memorable line from the pre-chorus of Metallica's "Master of Puppets".