From there +‎ by. Compare the parallel formation of German dabei.



thereby (not comparable)

  1. (formal) By it; by that; by that means, or as a consequence of that.
    • 1729, Jonathan Swift, A Modest Proposal:
      Thirdly, Whereas the Maintainance of an hundred thousand Children, from two Years old, and upwards, cannot be computed at less than Ten Shillings a piece per Annum, the Nation's Stock will be thereby encreased fifty thousand pounds per Annum, besides the profit of a new Dish, introduced to the Tables of all Gentlemen of Fortune in the Kingdom, who have any refinement in Taste, and the Money will circulate among our selves, the Goods being entirely of our own Growth and Manufacture.
    • 1787, United States Constitution, Article VI:
      This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.



See alsoEdit

Here-, there-, and where- words