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mundo m. (Noun) "world"
12th cent. From Latin mundus 'id.' Ultimately of unknown origin. According to de Vaan (2014), a connection to Etruscan munθ- "cannot be established as long as its meaning is unknown."
Indo-European
Romance
Asturian mundu, Portuguese mundo, Galician mundo, Catalan món, French monde, Italian mondo, Sardinian mundhu
Tyrsenian
munθ-?, meaning unknown

On the basis of Auto de Reyes Magos (12th cent.), it is believed that mundo was pronounced /mon.do/ for some time: Que es senior de todo el mundo / asi cumo el cilo es redondo. This conservative pronunciation was likely due to reinforcement from Ecclesiastical Latin and, perhaps, from Gallo-Romance languages like French, Catalan, which meant that for several centuries there were two pronunciations of mundo side-by-side.