Definition of "at bottom"
at bottom
prepositional phrase
(idiomatic) Really, basically, fundamentally.
Quotations
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.
1705, Daniel Defoe, The Consolidator: or, Memoirs of Sundry Transactions From the World in the Moon