I know it's a very common word. The etymology is “early 19th century (originally US): from Dutch baas ‘master’.”
You have managers, you have supervisors, you do not have a master. You do not have a “boss”. It cringes me out since based on my personal experience, the most boot licking employees (fuck you in particular Serena Rivera) use it to stroke the egos of managers.
For me, it also enforces a modicum of worker self-respect not to ever refer to anyone as my “boss”. Big props and a happy Monday to anyone who quits their job without notice, doesn't take any unwarranted bs from a supervisor, and/or stands up for themselves and demands a raise for being asked to take on additional responsibility. Never forget they NEED US to make them money. No one is your master.