mission (the noun): from "classical Latin missiōn-, missiō sending, dismissal, sending of ambassadors, . . . in post-classical Latin also ‘sending of Christ into the world’ (4th cent.), ‘sending of the Holy Spirit into the world’ (4th or 5th cent. in Augustine)", which is from classical Latin "miss- , past participial stem of mittere to send".
"mission, n." OED Online. September 2012. Oxford University Press. http://ezproxy.spu.edu/login?url=http://www.oed.com/view/Entry/119999 (accessed September 21, 2012).