Even if that's true, which I'm not sure it is, it doesn't necessarily mean that morals emerge from individual choice. Personally I think morals are emergent from groups.
Morals are an individual personal choice - derived from the word 'morales', which means 'custom'. Individuals adopt customs - both learned individually, and mores adopted from a group.
Ethics are a group choice - a set of morals, in the plural, derived from "ethike" - the 'science of morals'.
They're interlocked, sure, but it is an individual who makes a moral decision for themselves, but an ethical decision for their group...
EDIT: I mean, all you have to do is look at the definition of both words in a few dictionaries. Its pretty clearly stated that ethics are a group of morals formulated around the purposes of a group, where morals are derived from and based on an individual decision. Can't have one without the other.
Of course, you are within your rights to disagree - such is the nature of the ethics of philosophical discussions.
You've obviously defined it that way but I don't see why it's true. Your argument is essentially that morals emerge from individuals because of the etymology of the world moral. I don't find that very convincing.
