Hey. I screwed up. The earliest date for the word "missional" is not 1814, as I blogged last week. That was a bad OCR scan [BAD GOOGLE, NO COOKIE!!] and the word that gets cut off is actually "missionary" and NOT "missional". Thanks to Robinson Mitchell who had a library check the paper version. The earliest date for "missional" that I have found is a British book from 1883 and I have the actual book (1886) so I can confirm it. More here.
And that means the Brits coined the word and not the Yanks. One should know these things. Rule Britannia! God save the Queen!