Once again, I find tsuwm's wwftd very interesting. I have searched every way I can think
of, and have been unable to find its etymology. It just does not seem like a coinage that
Bowditch would have created. But where did he get it from? Many words ending in
"-tage" are of French origin, so I tried various spellings of first part of word, but had no luck.
Maybe some of you might enjoy trying to find origin of this word.

kumatage

A bright appearance in the horizon, under the sun or moon, arising
from the reflected light of those bodies from the small rippling
waves on the surface of the water FROM Bowditch´s Navigator,
24th edition (1854) page 295, thanks to John Lynch Cummins (moon
river)

-tsuwm http://home.mn.rr.com/wwftd/