How wonderful to find some scholarly interest in my question.
I want to make it clear that I am not insinuating that Tim and Alan or Heaney have mistranslated.
My question (or perhaps my suspicious, nagging wondering about how it fits in with facts, or what I think I know) goes beyond that. I was curious about the source word, so thanks, Peter so much for the link to the Nowell Codex.
Here is some further musing. (Just thinking out loud, not pretending to have cracked a Rosetta Stone.)
That there is only one extant copy of Beowulf, and that one is fire damaged, so we cannot ascertain its veracity.
That the whole set up of the poem is oral literature that has been written down (like the Iliad and Odyssey).
That the early church, the one a few centuries old, did its utmost to ruthlessly wipe out all traces of rival pagan beliefs.
That there are countless examples of manuscripts which exist in differing texts (not least the early gospels but also ancient texts in Hebrew).
That England was a bastion of Christianity during the span when the manuscript was made (eighth to eleventh century).
That the pagan Vikings were plundering Christendom until into the eleventh century.
That the Christianizing influences on (geographical) Sweden came from England (where it was established) in the ninth century. Whereas the influences of ditto on Denmark came from Germany and France and were earlier.
That these two religious spheres were in conflict with one another. Because the Christianizing of peoples was political, mandated in Scandinavia by convincing the kings that it was good for his power base and then the king told his people: convert or else. (This is contrary to popular belief which piously relies on the official propaganda.)
I happen to live in "Geat" and our history is very much alive being all around us. We have relics of early Christianity in our backyard, this being a seat of the early power struggles and later establishment. Everyone (well, lots of people anyway) knows the stories. This historical topic has long been an area of my particular, (if mostly amateur but sometime academic) study. So my question does not derive from an idle thought and a quick Google.
That there is hardly a bird that the Church has not added to its repertoire to use as a moral example. The pelicans, the crane, the raven, and many more are found inside churches as sculpture and also in legends--many, if not most, of which were retelling of pagan tales). This incorporation from other religions was a stock-in-trade trick to root out the old religions.
For instance, to veer somewhat, the Greek midsummer festivities (summer solstice) had the killjoy John the Baptist superimposed on them. What could be grimmer than to replace a carnal love feast with a celebration of that old ranter in the wilderness crying
repent, repent. The Swedish midwinter Yule became Christmas (and the hog still reigns supreme on the Yule table to the horror of our new Muslim citizens). I could digress here but will control myself.
That copyists do make mistakes, intentionally or inadvertently.
That it makes MUCH MORE SENSE that a blackbird is joyfully singing on the morning of departure for home, than that a raven is joyfully singing.
There seems to be agreement among scholars (as I found out through Ross's post, thank you) that this is a thorny point, that the text there doesn't quite make sense. So the academics are twisting themselves into pretzels trying to find ways to make it fit. (Rather like the old joke among the military: if the map and the terrain do not agree, trust the map).
But thanks lovely Spherians for interest. My question was impulsively asked, knowing that friend Tim was somewhere about and might be able to give me some scoop about why "raven" was his choice. His answer might well be: Because there is scholarly consensus about those source-target words.
My interest was especially piqued because I've just (coincidentally) enjoyed the series on the origins and spread of the English language (long one of my special areas of interest) which I've recommended on another thread yesterday. But here it is again should anyone be interested--8 hours in all.
https://www.youtube.com/watch?v=VsVz5U76kX0
I still think it is wrong--not wrongly translated, but that somewhere down the centuries the joyous song of the night-singing blackbird has been wrongly attributed or translated and become permanent.
But thanks again for all the thoughtful input on this.
I've written the above off thte top of my head before I have my morning coffee so may return (or not).
Now my morning java and continuing my read of this great saga. (FYI the Longman book contains much more than the Murphy-Sullivan translation of Beowulf.)