Sky and clouds

[Koontz John E]

On Fri, 16 Feb 2001 Rgraczyk at aol.com wrote:
> Crow has awa'xa for 'sky' and ahpaaxi' for 'cloud'.  Perhaps Hidatsa has lost
> the awa'xa term and uses ahpaaxi' for both 'clouds' and 'sky'.  Actually
> awa'xa looks like a better candidate for a cognate with the other Siouan
> terms.

Is there any process (e.g., "aku-" prefixation) that would derive ahpaaxi'
from awa'xa?

JEK