Other forms: mustered, mustering, musters
To muster is to gather people or courage together. Muster the troops, muster support, muster the courage.
The military sense is the original: a muster was the assembly of soldiers for inspection, and a muster roll listed who was present — which is where the phrase pass muster comes from, meaning good enough to be accepted. Figuratively you muster courage, energy, support or enthusiasm, always with effort implied. Note that all he could muster is the standard construction for falling short.
1verbmusterTo gather people together for inspection or action.
“The captain mustered the crew on deck to explain the change of course.”
2verbcourageTo gather courage or support with effort.
“She finally mustered the courage to ask her boss for a pay rise.”
muster is a gathering.
Anglo-Norman mostrer comes from Latin monstrare, to show. Demonstrate and monster come from the same showing — a monster was originally a portent, something shown as a warning.
Proto-Indo-European
*men-
Latin
mōnstrō — to show
Middle French
monstrer
Anglo-Norman
mostrer
Middle English
musteren
English, today
muster
Built from
From Middle English musteren, borrowed from Anglo-Norman mostrer, Middle French monstrer, moustrer (whence the noun monstre, which gave the English noun), from Latin mōnstrō (“to show”), from moneō (“to admonish”). Cognate with French montrer (“to show”), Italian mostrare (“to show”), Spanish mostrar (“to show”). See also monster.
Etymology from Wiktionary, CC BY-SA