This doesn’t add a whole lot to what you’ve already learned from others since posing your question, but I thought I would add some details for reference.
The Hildebrandslied, a much studied Old High German alliterative poem, was transcribed by a couple of eighth-century monks working from an earlier manuscript based on an oral recounting. (Lots could go wrong there, but that is for another question.)
Some translations of this work offer literal interpretations, not attempting to retain the meter or alliteration. Others, like that of Francis A. Wood, try to capture the effect of the original. Wood notes in his poem introduction that his translation “aims to give the spirit as well as the meter of the Hildebrandslied. . . . Though not a literal translation, it nevertheless closely follows the thought of the [Old High German] poem.” (Wood even makes up the lost ending.)
By comparing a literal translation with Wood’s, we can see that weirdwielder is Wood’s own fanciful, clever, need-some-Ws-stat nonce word (and a hapax legomenon).
To start, we can look at part of the OED entry (and an example usage) for weird the noun:
Etymology: Old English wyrd (feminine), = Old Saxon wurd (plural wurdi), Old High German wurt, Old Norse urð-r, from the weak grade of the stem werþ-, warþ-, wurþ- to become: see WORTH v.1
1. a. The principle, power, or agency by which events are predetermined; fate, destiny.
1895 W. MORRIS & A. J.
WYATT tr. Tale of Beowulf 17 Weird swept them away.
Source: Oxford English Dictionary (login
A number of other related definitions appear there—magical power, witchery, prophecy—but here, weird = fate. Note in the etymology worth (to come to be, come to pass, come about, happen, take place), as Wood plays with this in the line in question.
Next we can look at the original line of the poem in Old High German. Note the four alliterative Ws:
“welaga nu, waltant got [quad Hiltibrant], wewurt skihit.
This article brings up an interesting point: the Christianization of
“heathen” works. Those monks! Were it not for God’s appearance
elsewhere in Wood’s translation, I might have thought Wood was
re-heathenizing the work by turning God into a weirdwielder.
Compare this literal translation by Michaela Macha, who notes, “I have translated into free verse, staying literal where possible, not attempting to reproduce the original meter or alliteration.” Note the lone W:
“Well now, mighty god”, spoke Hildebrand, “sorrowful fate (woe wyrd)
Source: Historical & Classical Poetry ~
And here’s Wood’s interpretation. Note again: four Ws:
Great Weirdwielder, woe worth the day!
This is pretty tricky on Wood’s part. He turns the two-W wewurt + skihit—literally “woe fate happens”—into woe worth, meaning “woe be to.” Woe be to the day. Woe happens to the day.
Lest there be any question about the wurt/fate part, Wood leverages the Ws from welaga nu, waltant got (well now, mighty god) for a mashup of weird and wielder. A wielder of weird. A wielder of fate. Someone or something with the mighty power to control destiny.