It is a form of antiquated English. It is not commonly used these days but it can be found in historical texts and a few historical sayings/ phrases. Simply Maketh = Makes. "Good manners make a good man". Incidentally it is still used in English Biblical writings ... Maketh = Makes. Cometh =Comes ( Cometh the hour cometh the man).

"Maketh" is an old grammatical form in English that is no longer used. I think it is just the third person, used both in singular or plural. In this case it means "Manners make the man," which in turn means "good manners are the most important characteristic of an upper-class gentleman (=caballero? hidalgo? señor?) "Maketh" was still current at the time when Shakespeare wrote, and also when the famous King James translation of the Bible was made, in 1611. Literature and poetry from that era use it. The King James version is a landmark of English-speaking culture and literature. It is the English counterpart to the Reina-Valera in Spanish. Words ending in -eth are thus familiar to many modern speakers. It can sometimes be used to make something sound weighty or important. In the King James version, the famous Psalm 23 (Salmo 23) begins: "The Lord is my shepherd; I shall not want. He maketh me to lie down in green pastures: he leadeth me beside the still waters. He restoreth my soul: he leadeth me in the paths of righteousness for his name's sake." The same verse, in modern translation, reads: "The Lord is my shepherd, I shall not want; he makes me lie down in green pastures; he leads me beside still waters; he restores my soul. He leads me in paths of righteousness for his name’s sake." Thus, all the -eth ending are replaced by the normal modern -s ending, and there are a few other small changes to modernize the language.

It means "make", it is just that the phrase is very old, so it is originally in an older sounding English that is anachronistic now. It is like saying "he de hacer algo" in español instead of "tienes que hacer algo". It means the same thing, but one way is a bit more formal and dated.

Old English meaning 'to make'

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