Douglas Harper's Etymology Dictionary
1883, in architecture, "piece of a wall between two openings," as the central pillar of a great doorway," from French trumeau, literally "calf of the leg" (12c.), from a Germanic source (compare German Trumm "end, stump," Swedish dialectal tromm "stump, end of a log").
Wiktionary
n. 1 (context architecture English) The pillar or center post supporting the lintel in the middle of a doorway, especially in a church. 2 A trumeau mirror.
Wikipedia
Trumeau, in architecture, is the central pillar or mullion supporting the tympanum of a large doorway, commonly found in medieval buildings. It is often sculpted.
Usage examples of "trumeau".
Quennebert was well aware of the zeal with which the indefatigable Trumeau sought to injure him.
One morning in the beginning of February 1660, Trumeau called to see his cousin.
Quennebert, for his features lost their look of care, his wrinkles smoothed themselves out, till the guests, among whom was Trumeau, who did not suspect the secret of his relief from suspense, began to believe, despite their surprise, that he was really rejoiced at obtaining legal possession of the charming Madame Rapally.
She had just found and read a paper left on the bed by Trumeau, who before leaving had contrived to glide into the room unseen.
It was by the merest chance that Trumeau had come on the record of the marriage, and he now challenged his rival to produce a certificate of the death of his first wife.
In the short interval which ensued, and while Trumeau was hugging the knowledge of the discovery he had made, a stroke of luck had brought the pretended chevalier to La Constantin.
Marie-Jeanne Trumeau, the pregnant wife of a day laborer from the faubourg Saint-Antoine.
Marie-Jeanne Trumeau was reprieved by personal intervention of Reveillon himself.