From Old English 'blæd' (leaf), PIE *bʰleh₃- (to bloom) — the weapon sense grew from the leaf-like shape of a sword.
The flat cutting edge of a knife, sword, or other tool; a long, narrow leaf of grass or a cereal plant.
From Old English "blæd" ("leaf, blade of grass"), from Proto-Germanic *bladą ("leaf, blade"), from PIE *bʰleh₃-to- ("that which has bloomed"), a derivative of *bʰleh₃- ("to bloom, to flower"). The semantic path is leaf → flat cutting part of a sword or knife, transferred by visual analogy with a leaf's flat, extended shape. The Proto-Germanic root produced Old Norse