Bottom
.Goods imported in British bottoms are those which come in our own vessels.
At bottom. Radically, fundamentally: as, the young prodigal lived a riotous life, but was good at bottom, or below the surface.
—Ruskin: True and Beautiful, p. 426.
From the bottom of my heart. Without reservation. (Imo corde.)
“If one of the parties … be content to forgive from the bottom of his heart all that the other hath trespassed against him.”—Common Prayer Book.
He was at the bottom of it. He really instigated it, or prompted it.
“My ventures are not in one bottom trusted.”—Shakespeare: Merchant of Venice, i. 1.
To have no bottom. To be unfathomable.
To touch bottom. To reach the lowest depth.