etymology of hoppas

[Alan Hartley]

Has anyone run across the word hoppas/hoppis/hoppus? It's a a sort of
backpack and is cited in Mathew's Dict. of Americansms from 1803-26.
It's always in Indian or frontier contexts, so it might have a native
etymon. It might also be a variant of the English word hopper, a
receptacle carried on the back, used to carry seed for sowing, et al. A
nonrhotic variant is credible, but why the final -s? Its persistence is
a problem: one would expect at least occasionally forms like *hoppa or
*hoppe for r-less hopper, but they aren't given in dictionaries. Hoppas
occurs in 1791 in Amer. State Papers vol. IV (Indian Affairs vol. I)
(1832) p. 151 "You are just now rising from your seats, with your backs
bent, bearing your loaded hoppas." The Iroquois speaker here (in
translation) is apparently using the word in the plural, so it seems it
might be an r-less 'hopper'.

In the Lewis and Clark journals (vol. 4, p. 250), Meriwether Lewis
writes "I had now my sack and blanket happerst in readiness to swing on
my back". I take this to be a spelling of 'hoppused', meaning 'trussed
up or slung like a backpack'. (Happer is a Scots dial. var. of hopper.)
Again, though, if the word is really hopper, why doesn't Lewis write
'hoppered' or something similar?

I'd appreciate any etymological suggestions or further examples of the word.

Thanks,

Alan
--
Alan H. Hartley