The Yanks don't "take shelter" anywhere do they? They "hunker down". Where does this ridiculous term come from? What is a hunker? Do you have one in your collection? I went in a few BUNKERS yesterday, which meant the other guys had to "hunker down", out of harms way! Hunker?!!! Eh?!!
hmm eighteenth century
from huiken - that is pronounced with the first syllable rhyming with cow rather than boy
dunno how the en crept in
one would expect it to persist in American usage
as English follow the usual rules on mutation
the further away from the centre of a language it mutates more slowly ( and therefore also maintains older forms - gotten springs to mind) - seen also in Quebecois and Texan german