Ethics and morality are often used by philosophers as synonyms. Some philosophers have suggested that we use the words in slightly different ways, where “ethics” would refer to a system describing right and wrong action in particular contexts like a profession or a role (like “business ethics"); “morality” would describe rightness and wrongness in the more general role of being a human being (like “it's wrong to harm other human beings”). But, there may not be a sharp distinction between these contexts, and the words are often used interchangeably.
Principles are rules. In ethics, they are rules about right and wrong action, like “If a person is innocent, it is wrong to punish him/her (or, you should not punish him/her).”
Virtues are properties of people or other beings who act rightly in a habitual way. A habit of acting rightly is a virtue. A person who acts rightly may or may not be following a moral rule or principle. In fact, it may be possible to have a virtue without believing in any moral principles, or if no principles exist.
Etiquette is a set of rules for how to behave rightly or wrongly that are generally understood to be less serious than moral rules. One way of making the distinction is to say that societies can differ radically in their rules of etiquette without any negative consequences, but not in their rules of morality; on this approach, rules of etiquette are defined as the rules that can vary among societies without any bad moral consequences. So, no society that allows punishing the innocent is a moral society, and such a society may not be a stable society. But one society can make it right to pass people on the right, and another society can make it right to pass people on the left, as a matter of etiquette, and it doesn't matter — all that matters is that there is some standard for how passing should work.