Wapato (Sagittaria latifolia and its smaller cousin S. cuneata) was at one time a common plant in parts of the Columbia River and lakes in the Willamette Valley. It also used to grow in Tenmile Lake (and, I’ve heard still does, but does not seem to be common there these days), and there was a report 80 years ago of it growing in Siltcoos Lake (and maybe still does). And a tribal youth canoe trip rediscovered a lovely patch in the Umpqua River.
There is an interesting article in Keeping it Living about lower Columbia peoples and wapato. It was a very important food for many Indian people and there were many villages located next to large patches of it. The article also mentions a potential origin for the word ‘wapato’, which came from Chinook jargon. A lot of jargon words came straight from Chinook, but ‘wapato’ might be an interesting hybrid of Tualitin Kalapuya and Clackamas Chinook. Clackamas has noun prefixes wa- for feminine and i- for masculine. The Clackamas noun stem for wapato is qat, prefixed with wa- so it always looked like waqat. The Tualitin word for wapato is mamp-du. At some point, the prefix wa- got attached to mamp-du (wamampdu) and eventually got changed to wapato (perhaps by English speakers who always had a hard time with Northwestern Indian languages).
The words for wapato in the Coosan and Siuslaw languages are essentially identical to each other, but definitely not borrowed from Chinook or Tualitin. Hanis is kwii’mits, Milluk and Siuslaw qwii’mits. It is unusual for all 3 languages to have more or less the same word for something (I can only think of one other at the moment, crow. Crow in Hanis and Milluk is maqatl and maqtl in Siuslaw). But kwii’mits/qwii’mits definitely was not borrowed from Chinook or Tualitin!