What is the meaning of “runneth”?
What is the meaning of “runneth” in My Cup Runneth Over?
“runneth” is the Early Modern English third person singular of “run” (suffix -th, written -eth after consonants, and the consonant doubled). So, it would be “runs over” in Modern English, i.e. “overflows”. As noted in the link in your question, this quotation means “I have more than I need”.
It means 'runs over' i.e overflows