Mainstream philosophy translation: moral concepts rigidly designate certain natural properties. However, precisely which properties these are was originally fixed by certain contingent facts about the world we live in and human history.

Hence the whole "If the world had been different, then what is denoted by "morality" would have been different, but those actions would still be immoral (given what "morality" actually denotes)" thing.

This position is sometimes referred to as "sythetic ethical naturalism".