The word is partly formed within English and partly by a later borrowing from early Scandinavian. Its earliest sense named a boundary. One of its oldest surviving uses in English is in King Ælfred's own translation of Boethius, written in the late ninth century. Widsith, an Old English poem, uses it for the line King Offa of Angel, a legendary ruler of the continental homeland of the Angles, cut with a sword against the Myrgings, a rival Germanic people, at the River Eider on what is now the German-Danish border. Three Germanic words lie behind it, kept separate for centuries before finally merging in Middle English.
Danish settlers reached eastern and northern England from the ninth century onward, in the region that became the Danelaw, bringing a closely related form of the word with them. It reinforced two English words already in use, one meaning boundary, one meaning sign. Geoffrey Chaucer used the word in his Parson's Tale, written around 1390, pairing it with the idea of chastity.
Behind the English word lies a Proto-Indo-European root, *merg-, meaning boundary or border, though not every scholar agrees the connection is certain. The same root gave its name to the Marcomanni, a Germanic people whose name meant border folk, recorded by the Roman historian Tacitus in his Germania around 98 AD, who were later locked in decades of war against Rome under the emperor Marcus Aurelius. Latin margō, the edge or brink of something, may also share the same distant ancestor.
MARCH and MARGIN share the same distant root. MARCH, a word for a border region, entered English in the early thirteenth century from Old French marche, from the same ancient Germanic root as the English word, two languages drawing on one shared ancestor. MARGIN traces back to classical Latin margo, meaning the edge of something. Scholars agree the two words are probably related, but cannot agree on what their common ancestor was.
By the eighteenth century the word had taken on a very practical use aboard ship. A knotted line, its intervals measured out in advance, was lowered into the water so a sailor could call out the depth beneath the hull, and a call of two units meant safe water for a riverboat. American writer and humorist Samuel Langhorne Clemens took his pen name from that same river cry, a call he had heard many times as a young Mississippi pilot before he ever published a word.
