In his attempts to elucidate Church History in Plain Language, Bruce Shelley says,
“The word “person,” however, did not mean to the early Christians what it means today. To us, a person means someone like Tom, Dick, or Harry. But the Latin word persona originally meant a mask worn by an actor on the stage. In Trinitarian thought the “mask” is not worn by God to hide but to reveal his true character. It is clear that when we think of the Trinity, we should not try to think of three persons in our sense of the term, but three personal disclosures of God that correspond to what he is really like.”
Shelley, Bruce L. Church History in Plain Language. Updated 2nd ed. Dallas, Tex.: Word Pub., 1995.