Why does the Valkyrie call the raven “the skull picker of Hymir” in Hrafnsmál?

Question

At the beginning of Hrafnsmál the Valkyrie calls the raven "the skull picker of Hymir":

1. Hearken, noblemen, while I celebrate Harold the magnificent and his feats of arms. I will tell of the words which I heard spoken by a maiden fair and golden haired as she held converse with a raven.

2. The valkyrie prided herself on her wisdom ; — and the warlike maid took no pleasure in men, for she knew the language of birds. With white throat and sparkling eyes she greeted the skull picker of Hymir as he sat on a jutting ledge of rock,

3. 'How is it with you, ye ravens? Whence are ye come with bloody beak at the dawning of day? Torn flesh is hanging from your talons, and a reek of carrion comes from your mouths. I doubt not that ye have passed the night amid a scene of carnage.'

_{Source: Anglo-Saxon and Norse Poems. Edited and translated by N. Kershaw.}

Is this a reference to the giant Hymir (and his unusually hard skull)?

Answer 1

The original text:

Vitr þóttisk valkyrja;

verar né óru þekkir

feimu inni framsóttu,

es fugls rǫdd kunni.

Kvaddi in kverkhvíta

ok in glæ*hvarma

Hymis hausreyti,

es sat á horni of bjarga.

The valkyrie thought herself wise; men were not pleasing to the aggressive maid, who understood the voice of the bird. The white-throated and the bright-eyelashed one greeted the skull-picker of Hymir [RAVEN], which sat on the edge of a cliff.

From the footnotes:

— [7] hausreyti Hymis ‘the skull-picker of Hymir [RAVEN]’: Hymir is an adversary of Þórr and subject of the late eddic poem Hymiskviða (and SnE 2005, 44-5), but on what occasion a raven picked flesh from the skull of Hymir is unknown. There may be confusion with the primeval giant Ymir, from whose skull the sky was made (Vafþr 21, 28, Vsp 3, Arn Magndr 19/4II; SnE 2005, 10, 11, 12, 15, and 170 on confusion between Hymir and Ymir in mss). Kock (NN §1024) accordingly emends to Ymis here, also reversing the order of the words for the sake of the alliteration