We can look back to the early theories of ethics from Socrates and later Kant and others having to do with general moral and ethical behaviours for humans. And then as business and professions began to evolve there was reference to ethic practice of trades, and of professional societies as they developed (accountants, lawyers, etc). Indeed, much of coaching today has borrowed from the concept of Socratic dialogue, but remember, he was sentenced to death by poison essentially for upsetting the community by teaching young persons to ask a lot of questions of themselves and their parents. You can imagine how that went over in early Greek society.
Nevertheless, we can look to Socrates as an early coach of sorts and later on Aristotle as well. Both men set the stage for all ethical guidelines that evolved in professions over centuries (See Ethical Maturity in the Helping Professions, Carroll and Shaw)
Five Sources of Ethical Standards
The Utilitarian Approach
Some ethicists emphasize that the ethical action is the one that provides the most good or does the least harm, or, to put it another way, produces the greatest balance of good over harm. The ethical corporate action, then, is the one that produces the greatest good and does the least harm for all who are affected-customers, employees, shareholders, the community, and the environment. Ethical warfare balances the good achieved in ending terrorism with the harm done to all parties through death, injuries, and destruction. The utilitarian approach deals with consequences; it tries both to increase the good done and to reduce the harm done.