What about *xraina- < *kWrói[h2]-no- 'something valuable' from the root
*kWreih2- 'buy' (converse of 'livestock' --> 'wealth', as in <feoh> or
<pecu:nia>)? It could be compared to OLith. krieno (gen.), Latv. kriens
'price for a bride' (which, incidentally, was often paid in cattle, and
among the old Finns and Saami in reindeer). The root seems to be
otherwise unattested in Germanic, but as it occurs in Celtic and
Balto-Slavic (not to mention other branches), the absence may be due to
relatively late lexical replacement of the old verb by the relatives of
<buy> and <kaufen> (the latter, borrowed from Germanic, has almost
ousted the native reflexes of *kWreih2- from Slavic).
Piotr