A fascinating little research paper, titled 'A Runic Prayer' by Dominika Skrzypek, into the usage of the runes in early Christianised Scandinavia can be found HERE.
I spent many of my childhood years in Täby, Uppland (Swedish region mentioned in the paper), the municipality known for having the most of these Christian rune stones, so reading this makes for time travel in more than one way!
There are a couple of things that I don't agree with in this research. Firstly, I don't believe the runes were 'inspired' by the Greek and/or Etruscan alphabets - I believe their origins predate both of those though I'm aware this is hard to prove.
Secondly, the word and/ond/od/at (spirit) was most definitely not introduced to fit with Christian theology - It existed as a concept long before the first Christian missionaries came to Scandinavia.
If anything the pre-Christian Heathen view of the parts that make up a human was more complex than the Christian view. This is not difficult to prove and you can find a really good breakdown of the Heathen philosophy HERE.
That said, I recommend this paper for the multiple examples of rune stones commemorating the dead in a society still in flux between Heathen and Christian culture.
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