Since it appears to refer to a part of Anglo-Saxon drinking ritual, it has commanded a lot of scholarly attention.
The noble hall broke into a din; the Danes all were, the citadel-dwellers each of the bold, earls in the flood of bitter drink[1] Slade in a footnote states that "the kenning (if it is one) is obscure".
Klaeber conjectures that "-scerwen, related to *scerwan 'grant', 'allot' (bescerwan ='deprive') - 'dispensing of ale', or, in a pregnant sense, of 'bitter or fateful drink' might have come to be used as a figurative expression for 'distress'".
Tolkien also argues for the "deprivation of ale" interpretation and connects it to the word "meoduscerwen" (which is similarly translated as "dread" or "horror") in the poem Andreas.
[2] Irving (1963) reads ealuscerwen as 'pouring of ale': "In Beowulf the tremendous din made by Grendel, first in struggling with Beowulf and later in roaring with pain and fright, seems to have reminded the poet of the ordinary or conventional occasion for such loud noise in a hall--a drinking party.