On: Every character has a story: U+213a (rotated Q) (2...

[asveikau]

I believe the reason corpus changes the root when you decline it is because Latin went through a phase where /s/ between vowels became /r/.

Eg: corpus -> * corpusem -> corporem

Similar pattern with many other Latin words we think of as ending in -r but the nominative form actually has an -s, eg. colos -> * colosem -> colorem

[thaumasiotes → asveikau]

colos is an archaic form; standard Latin has color.

[asveikau → thaumasiotes]

Ok. But the thing I am going for is the pattern where we think of descendants of the word having /r/. colos does fit the pattern. As would flos.