The history of the word grace is curious.  We are apt to confuse it with the Latin gracilis (slender), with which it has no connection, and which only in later times acquired the sense of elegant, whereas it originally meant lean, or wasted, and came from a kindred word to the Greek γράω (grao), to consume.
    Grates, on the contrary, were thanks, whence what was done gratiis, or gratis, was for thanks and nothing else, according to our present use of the word—whence our gratuitous.  So again gratus applied to him who was thankful, and to what inspired thanks; and gratia was favour, or bounty, and was used to render the Greek χάρις; and thus have the Greek Charities come down to us as Graces.  Then, too, he was gratiosus who possessed the free spirit of bounty and friendliness, exactly expressed by our gracious; but, in Italy, it was degraded into mere lively good-nature, till un grazioso is little better than a buffoon; and gracieux in France means scarcely more than engaging.
    Gratia was used by early Latin writers for divine favour, whence the theological meaning of grace.  And from grates (thanks) comes our expression of "saying grace before meat."
    The English name of Grace is intended as the abstract theological term, and was adopted with many others of like nature at the Reformation.  Its continuation after the dying away of most of its congeners is owing to the Irish, who thought it resembled their native Grainé (love), and thereupon adopted it so plentifully that Grace or Gracie is generally to be found wherever there is an Irish connection. (History of Christian Names, Yonge, 1884)