The Spanish word for “mustache” is bigote. The English word for “a person intolerant of those of different religions, race, or politics” is bigot. Obviously there’s some sort of relationship between the two words.
In 1483, Holy Roman Emperor Charles V arrived in Spain with German-speaking Swiss Guards. They were noted for their impressive mustaches and their tendency to say “bei Got!” (“By God!”). Spaniards began to use bigot first as a name for them and later for their memorable upper-lip hair. The word eventually became Hispanicized into bigote, pronounced “bee-GO-tay.”
The English word is about a century younger. The French Beguines, a Catholic lay sisterhood, also had a tendency to say “by God,” but they were noted for their excessive and hypocritical devotion. The word bigot was coined in French with the sense of a foolishly obstinate or opinionated person. The world crossed the Channel and became part of English. Eventually the stress came to fall on the first syllable and the opinion came to be centered on intolerance.
When words migrate from one language to another, they don’t always arrive safely.