Stephen is “pleres charitos kai dynameos”, which literally means “full of grace and power”.
Mary’s “full of grace” is the Greek word “kecharitomene”, which, as a form of address, is unique to her in the entire Bible. It is a perfect tense (past tense for something totally accomplished), passive mood participle (with some kind of special features, IIRC). So it means something like “totally graced one.”
As something other than a form of address, and in the masculine form of the dative case (“kecharitomeno”) the word does appear in the Septuagint version of Sirach 18:17, which book most Protestants don’t think is part of the Bible. It is part of a book which was written as proverbs, but Christians can see, in the relevant section before the verse, a Christological context of prophecy.
*He that liveth for ever created all things together. God only shall be justified, and he remaineth an invincible king for ever. Who is able to declare his works? For who shall search out his glorious acts? And who shall shew forth the power of his majesty? or who shall be able to declare his mercy? Nothing may be taken away, nor added, neither is it possible to find out the glorious works of God: When a man hath done, then shall He begin: and when He leaveth off, [a man] shall be at a loss.
What is man, and what is his grace? and what is his good, or what is his evil? The number of the days of men at the most are a hundred years: as a drop of water of the sea are they esteemed: and as a pebble of the sand, so are a few years compared to eternity. Therefore God is patient in them, and poureth forth his mercy upon them. He hath seen the presumption of their heart – that it is wicked, and hath known their end – that it is evil. Then shall He begin. God is so great and incomprehensible, that when man has done all that he can to find out his greatness and boundless perfections, he is still to begin: for what he has found out, is but a mere nothing in comparison with his infinity.
Therefore hath He filled up His mercy in their favour, and hath shewn them the way of justice. The compassion of man is toward his neighbour: but the mercy of God is upon all flesh. He hath mercy, and teacheth, and correcteth, as a shepherd doth his flock. He hath mercy on him that receiveth the discipline of mercy, and that maketh haste in his judgments.
My son, in thy good deeds, make no complaint, and when thou givest any thing, add not grief by an evil word.
Shall not the dew assuage the heat? so also the good word is better than the gift.
Lo, is not a word better than a gift? but both are with a justified man.*
“A justified man” (homine justificato) is how the Hebrew, and how the Septuagint’s “kecharitomene”, is translated at this point in the Vulgate. (Jerome of course gave precedence to the Hebrew, but I don’t know right off the top of my head if he did this part of the Vulgate.) The various Protestant translations go with “the gracious man” or the like.
But the connection here is with God granting mercy to His people, doing wonderful things, with Sirach’s son (also named Jesus, btw) making no complaint in his good deeds, with dew (dew on the fleece is an image of Jesus’ incarnation into Mary’s womb), and the Word.
So you could translate this verse prophetically as “Lo, is not the Word better than the gift? But both are with/to the Kecharitomeno.”
This is an interesting interpretation, because it says that “completely grace-filled” is a word suitable to use as a title for Jesus Christ, as well as Mary. But any way you slice it, it’s a very interesting foreshadowing of the Annunciation.