early 14c., "agreement between persons, union in opinions or sentiment, state of mutual friendship, amiability," from Old French concorde (12c.) "concord, harmony, agreement, treaty," from Latin concordia "agreement, union," from concors (genitive concordis) "of the same mind," literally "hearts together," from assimilated form of com "with, together" (see con-) + cor (genitive cordis) "heart," from PIE root *kerd- "heart." Related: Concordial.
Meaning "a compact or agreement" is from late 15c. The village in Massachusetts (site of one of the opening battles of the Revolutionary War, April 19, 1775) was named in 1635, perhaps in reference to the peaceful dealings between the settlers and the local native tribes. The capital of New Hampshire was renamed for the Massachusetts town in 1763 (formerly it had been Pennycook, from a mangling of a native Algonquian word meaning "descent").
By the rude bridge that arched the flood,
Their flag to April’s breeze unfurled,
Here once the embattled farmers stood
And fired the shot heard round the world.
[Emerson, from "Concord Hymn"]
The Concord grape was so called by 1853, from the Massachusetts town, where it was bred for the local climate and promoted by farmer Ephraim Wales Bull. It is mentioned, but not named in the "New England Farmer" of Oct. 26, 1850, in its acknowledgements:
From E. W. Bull, Concord, a lot of fine seedling grapes, which he produced by a cross of the Catawba with a native grape. It is very good, and partakes of the nature of its parents, having some of the vinous flavor of the Catawba, and a little of the acid peculiar to our native fruit.