"mountain boomer"

[Jesse Sheidlower]

The term "mountain boomer" has a few senses referring to various types
of animals (the red squirrel, the mountain beaver, and the collared
lizard), and a sense referring to people, = 'hillbilly'. This sense
only slightly postdatess the 'red squirrel' sense.

Does anyone have an idea about the derivation of the 'hillbilly'
sense? The quots in DARE (from Kephart, and a LAGS informant) link it
to the 'squirrel' sense, but since these quots are so much later than
either word arose, it could just be a later association with the
common squirrel word; I don't know if we can actually assume that the
'hillbilly' sense is a transferred application of the term for a
squirrel. And what about the _boomer_--DARE suggests (s.v. "boomer,"
which used alone postdates "mountain boomer" by 20 years) that it's
from standard _boom_ 'to make a hollow sound', but surely the
squirrel, or the beaver or the lizard, doesn't make such a sound.

Thanks.

Jesse Sheidlower
OED