The verb elope means to run away secretly in order to get married. (It seems to be etymologically related to leap and to the Dutch and German verbs lopen and laufen, meaning to walk, to go, to run.)

The Anglo-Norman form aloper was originally a legal term meaning, of a wife, to run away from her husband with a paramour. For example, the Year Books of the Reign of King Edward III contain, for the year 1338:

En bref de dower plede fut qil [= ele] alopa de soun baroun en tiel ville en tiel counte, nient recounseil en la vie soun baroun, jugement &c. — Avant issue parle fut dount pais vendra, qe lalopement fuit alegge en autre counte qe la dowere ne fut demande.
     translation:
In a writ of Dower it was pleaded that she eloped from her husband in such a vill in such a county and was not reconciled during the life of her husband; judgment &c. — Before issue it was debated whence the Jury should come, for the elopement was alleged in a different county from that where the dower was demanded.

The noun elopement was defined, in Anglo-Norman and in English, in Les Termes de la Ley: or Certaine difficult and obscure Words and Termes of the Common Lawes and Statutes of this Realme now in vse expounded and explained (London, 1636), by John Rastell (circa 1475-1536) and his son, William Rastell (circa 1508-1565):

     [in Anglo-Norman – verse in Latin]
Elopement est quaunt feme espouse departa de son baron oue vn adulterer, & oue l’adulterer demurra sauns voluntarie reconcilement a sa baron, per ceo el perdra sa Dower per le Statute đ Westmonast. 2. cap.34. sur que vn Verse ad estre fait en cel manner:
          Sponte virum mulier fugiens, & adultera facta,
          Dote sua careat, nisi sponso sponte retracta.
     [in English]
Elopement is when a married woman departeth from her husband with an adulterer, and dwelleth with the adulterer without voluntary reconcilement to her husband, by that she shall lose her dower by the Statute of Westm. 2. cap.34. whereupon a Verse hath been made in this manner:
          The woman that her husband leaves,
          And in adultery leads her life,
          If that he dye vnreconcil’d,
          The Law endoweth no such wife.

(The word paramour is from Old French par amour, by love, which, in English, was written from an early date as one word and came to be treated as a noun.)

A WELL-KNOWN ELOPEMENT

This drawing from The Illustrated London News of 4^th January 1964 shows the Sandhill, in Newcastle upon Tyne, Northumberland, with the Guildhall on the left. The timber-framed house in the centre is known as Bessie Surtees House. One of the tenants was Aubone Surtees, whose daughter, Elizabeth ‘Bessie’ Surtees (1754-1831), eloped in 1772 from a first-floor window with John Scott (1751-1838), a coal merchant’s son. They ran away to Scotland where they were married (and were remarried in Newcastle after the families were reconciled). Scott eventually became a successful lawyer and, as Lord Eldon, Lord Chancellor of England.