Conventional understanding is that ‘mass’ comes from the dismissal at the end of mass (the Latin for mass is missa). I find it strange to name something after the point of conclusion when the mass is no more.
It may be more appropriate that the dismissal refers to the dismissal of catechumens after the Liturgy of the Word, as is currently practiced by the Eastern Rites. Dismissing the catechumens means that the real part of the mass of the faithful now begins.
Am I correct?