Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
MIDDLEMISS
As described in historical dictionaries
Patronymica Britannica (1860)
MIDDLEMISS. A corruption of Micliaelmas, which is so pronounced in some dialects. Other corrupted forms of the word, employed as surnames, are Middlemist and Middlemast. Pi-obabl)' from the person having been born at that festival. So Christmas, Easter, Pentecost, &c.
Origin: Celtic
Region of origin: British Isles
Country of origin: Scotland
Religion of origin: Christian
Language of origin: Gaelic