Then Beleg chose Anglachel; and that was a sword of great worth, and it was so named because it was made of iron that fell from heaven as a blazing star; it would cleave all earth-delved iron. One other sword only in Middle-earth was like to it. That sword does not enter into this tale, though it was made of the same ore by the same smith; and that smith was Eöl the Dark Elf, who took Aredhel Turgon's sister to wife. He gave Anglachel to Thingol as fee, which he begrudged, for leave to dwell in Nan Elmoth; but its mate Anguirel he kept, until it was stolen from him by Maeglin, his son.
But as Thingol turned the hilt of Anglachel towards Beleg, Melian looked at the blade; and she said: 'There is malice in this sword. The dark heart of the smith still dwells in it. It will not love the hand it serves; neither will it abide with you long.'
'Nonetheless I will wield it while I may,' said Beleg.

(Silm, Chapter 21, Of Túrin Turambar)

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.
...
Then quickly curtained with its covering pelt
was the lantern's light, and leaping Beleg
with his sword severed the searing bonds
on wrist and arm like ropes of hemp
so strong that whetting;..

(HoME III, The Lays of Beleriand, Túrin Son of Húrin & Glorund the Dragon, 1219-1223, 1230-1234)

Beleg drew his sword Anglachel, and with it he cut the fetters that bound Túrin; but fate was that day more strong, for the blade slipped as he cut the shackles, and Túrin's foot was pricked. Then he was aroused into a sudden wakefulness of rage and fear, and seeing one bending over him with naked blade he leapt up with a great cry, believing that Orcs were come again to torment him; and grappling with him in the darkness he seized Anglachel, and slew Beleg Cuthalion thinking him a foe.
...
And Gwindor gave the sword Anglachel into his hands, and Túrin knew that it was heavy and strong and had great power; but its blade was black and dull and its edges blunt. Then Gwindor said: 'This is a strange blade, and unlike any that I have seen in Middle-earth. It mourns for Beleg even as you do.

(Silm, Chapter 21, Of Túrin Turambar)

The sword Anglachel was forged anew for him by cunning smiths of Nargothrond, and though ever black its edges shone with pale fire; and he named it Gurthang, Iron of Death.

(Silm, Chapter 21, Of Túrin Turambar)

Anglachel - The sword made from meteoric iron that Thingol received from Eöl and which he gave to Beleg; after its reforging for Túrin named Gurthang. 247, 253-57

anga - 'iron', Sindarin ang, in Angainor, Angband, Anghabar, Anglachel, Angrist, Angrod, Anguirel, Gurthang; angren 'of iron' in Angrenost, plural engrin in Ered Engrin.

lhach - 'leaping flame' m Dagor Bragollach, and probably in Anglachel (the sword made by Eöl of meteoric iron).

(Silm, Appendix)