E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Blade.
A knowing blade, a sharp fellow; a regular blade, a buck or fop. (Anglo-Saxon, blad or bld, a branch or sprig.)
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Bld = branch, whence fruit, prosperity, glory, etc. The compound, Bld-dg = a prosperous day; bld-gifa, a glory-giver, i.e. a king, a regular blade.