Since photosystem II occurs before photosystem I, why are they not named in reverse?

My answer:
Historically photosystem I was named one since it was discovered before photosystem II but this does not represent the order of the electron flow. Also, some bacteria that produce no oxygen during photosynthesis lack photosystem II. These results hints at the suggestion that the splitting of water is coupled to photosystem II and that photosystem I developed earlier in evolution.
if not can you add on to what i have
thanks!

Since this is not my area of expertise, I searched Google under the key words "photosystem I II" to get these possible sources:

http://en.wikipedia.org/wiki/Photosystem
http://student.ccbcmd.edu/~gkaiser/biotutorials/photosyn/ldr.html
(Broken Link Removed)

I hope this helps. Thaqnks for asking.