Origins
The word 'grace' is one of the most semantically rich words in the English language, carrying simultaneous meanings in aesthetics (elegant movement), theology (divine favor), and social life (courteous goodwill) — and all three senses are etymologically authentic, traceable to the same Latin source. It enters Middle English from Old French 'grace' (favor, thanks, kindness, elegance), from Latin 'grātia' (favor, goodwill, regard, thanks, pleasing quality, charm), from 'grātus' (pleasing, agreeable, thankful), from PIE *gʷerH- (to praise, to welcome, to favor).
Latin 'grātia' already contained the full semantic range that 'grace' exhibits today. In Roman usage, 'grātia' meant the pleasing quality in a person or thing (charm, elegance), the goodwill shown by a patron to a client (favor, patronage), and the thanks owed by the recipient (gratitude). The Three Graces of Greek and Roman mythology — Aglaea (Splendor), Euphrosyne (Mirth), and Thalia (Good Cheer) — were personifications of the social and aesthetic dimensions of 'grātia': beauty, generosity, and the joy they produce.
Christian theology adopted 'grātia' as the central term for God's unmerited favor toward humanity. In the writings of Paul and, later, Augustine, 'grātia' became the word for the divine gift that humans cannot earn — salvation offered freely, not as a payment for virtue but as an act of pure generosity. This theological sense gave English the phrases 'grace of God,' 'state of grace,' 'fall from grace,' and 'grace period' (originally the time God allows for repentance). The prayer before meals called 'grace' is a 'grātia' — a thanksgiving.
French Influence
The root 'grātus' (pleasing, thankful) generated an enormous English word-family. 'Grateful' (from Latin 'grātus' + English '-ful') means 'full of thanks.' 'Gratitude' (from Latin 'grātitūdo') is the state of thankfulness. 'Gratis' (free of charge) is the ablative plural of 'grātia' — literally 'out of favor,' meaning 'as a gift, without expectation of payment.' 'Gratify' (to please). 'Ingrate' (an ungrateful person). 'Congratulate' (from Latin 'congratulārī,' to wish joy together — from 'con-' + 'grātulārī,' to show joy, from 'grātus'). Even 'agree' (from Old French 'agréer,' to receive with favor, from 'à gré,' to one's liking, from Latin 'grātum') belongs to this family.
The aesthetic sense of 'grace' — physical elegance, fluidity of movement — has proved remarkably durable. A 'graceful' dancer moves as if movement costs no effort; a 'graceful' sentence flows without strain. This sense connects to the theological one through the concept of effortlessness: divine grace, like physical grace, is given freely and received without struggle. The opposite, 'disgrace' (from Italian 'disgrazia,' loss of favor), describes the loss of both social standing and divine approval.
The word appears in some of the most quoted lines in the English language. John Newton's hymn 'Amazing Grace' (1772) — written by a former slave trader who experienced a religious conversion — uses the word in its full theological weight: grace as the undeserved gift that saves. The title alone captures the paradox that defines the word: grace is amazing precisely because it is unearned.