mitto

Mitto, mittere, misi, missum, third conjugation. The double t of the present stem reduces to a single s-heavy perfect and supine, misi and missum, and it is the supine that colonised English: mission, missile, message, missive, and with prefixes dismiss, permit, admit, submit, commit, promise.

The second sense is the older one. Mitto is to let go, and only by extension to send off; manu mittere, to let go from the hand, is how a Roman freed a slave, hence manumission. Missio is a discharge from the army before it is anything to do with a task. The ecclesiastical missa, the Mass, comes from the dismissal at the end of the service, ite, missa est, which is a fair reminder that the church did not always name things for the important bit.