At Bottom Meaning

(idiomatic) Really, basically, fundamentally.

Example: 1705, Daniel Defoe, The Consolidator: or, Memoirs of Sundry Transactions From the World in the Moon:
  They concerted Matters, and all at once fell to selling off their Stock, giving out daily Reports that they would be no longer concern'd, that it was a losing Trade, that the Fund at bottom was good for nothing.
1883, Robert Louis Stevenson, Treasure Island, ch. 16:
  I know you are a good man at bottom.
1907 July 5, Mark Twain, Chapters from My Autobiography, ch. 23:
  At bottom I supposed that he had mistaken another book for mine.
1947 Jan. 6, "The 80th Congress," Time (retrieved 26 June 2015):
  As the New Year opened, the survival of Western democracy rested, at bottom, on the case the U.S. would make for it.
2015 June 20, Michael Lewis, "Harvard Admissions Needs ‘Moneyball for Life’," New York Times (retrieved 26 June 2015):
  At bottom, he does not accept any authority higher than himself.