This old English word appears just once in the King James Version.
…my master left me, because 3 days agone I fell sick. —1 Samuel 30:13 KJV
Modern English Bible translations do not use the word “agone” at all—generally preferring “ago.”
In the above verse, the original Hebrew manuscripts do not contain a word for “ago.” This word is simply clearly inferred by the context, and added by translators to make the Ancient Hebrew phrasing more understandable to English readers.