Beleg's whetting spell
This article describes a concept which is mentioned in J.R.R. Tolkien's works, but was never given a definite name.
Beleg's whetting spell is a magic song according to the early version of the legendarium in The Lay of the Children of Húrin. The spell mentions several and mysterious concepts that would never appear in other works by J.R.R. Tolkien.
After Túrin had been captured by Orcs, his friend Beleg and the Gnome Flinding rescued him from the enemy's camp while he was still chained and unconscious. Once they took him nearby, Beleg sought his sword to cut Túrin's chains, but whispering magic songs to sharpen it:
There wondrous wove he words of sharpness,
and the names of knives and Gnomish blades
he uttered o'er it: even Ogbar's spear
and the glaive of Gaurin whose gleaming stroke
did rive the rocks of Rodrim's hall;
the sword of Saithnar, and the silver blades
of the enchanted children of chains forged
in their deep dungeon; the dirk of Nargil,
the knife of the North in Nogrod smithied;
the sweeping sickle of the slashing tempest,
the lambent lightning's leaping falchion
even Celeg Aithorn that shall cleave the world.
Then whistling whirled he the whetted sword-blade
and three times three it threshed the gloom,
till flame was kindled flickering strangely
like licking firelight in the lamp's glimmer
blue and baleful at the blade's edges.
—The Lay of the Children of Húrin, "II. Beleg", vv. 1207-1223
As Christopher Tolkien comments, the spell over the unnamed sword (later Anglachel) is an element that only appears in the Lay. It resembles Lúthien's 'lengthening spell', but there is no trace elsewhere of the mysterious characters and weapons mentioned by Beleg: Ogbar, Gaurin, Rodrim, Saithnar, Nargil and Celeg Aithorn.