The term martial comes from Mars, the Roman god of war.[...] Dictionary.com defines martial as “of, suitable for, or associated with war or armed forces” [...] [My question is]
To what degree are kata suitable, associated or appropriate to warfare?

I think that when you look at the older material out there, it becomes clear that kata were, at one time, primarily methods for training to be physically prepared for the ancient (pre-modern weapon) battlefield. By 'physically prepared' I mean both on a conditioning (stamina) level, and on a 'technique' level. These 'kata's' were almost certainly different from anything taught now, but they would still have some movements (horse stance being a likely one) that would be recognizable. So in this sense, yes they are 'martial' as they are "associated with war or armed forces." Yes, they are mostly associated the war of a past time, but so is modern military drills and marching, and that is still considered 'martial'.


My question here is limited to the extent that the Chinese kata that were passed down in Okinawa may have had martial or military origins in China.

Difficult to prove in terms of specific kata, I would imagine. But the movements and technique's in those kata are seen in much earlier depictions, so I would say the chances of Okinawan kata having been influenced in a large way via the somewhat circular and obscure route of early Chinese 'kata' (using the term fairly loosely here) is a good one. Of even more interest to me is going even earlier than that, but it murkier and murkier the further back you go. However, I do think that ancient Greece (possibly preceded by developments in the Near East) will be your eventual 'stop' point if you continue to trace this back further and further.

"Seek not to follow in the footsteps of the men of old; seek what they sought."