I will give you that to boot, i.e. in addition. The Anglo-Saxon boot or bot means “compensation.” (Gothic, bôta, profit.)
“As anyone shall be more powerful ... or higher in degree, shall he the more deeply make boot for sin, and pay for every misdeed.” —Laws of King Ethelred.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894