Aha! This entry from the Spanish edition of Wiktionary explains the word amuayu! So amun means 'I go', amuan means 'I will go', amuyu means 'the two of us go', and amuayu means 'the two of us will go'.
This blog post says that the word for 'who' in some region(s?) is [iˈŋi] - or is that a mistake and should that be [iˈɲi]? - rather than [iˈnej] (or even [iˈɲej]! This is like the whole [laˈmwen] ~ [lamˈŋjen] ~ [lamˈŋen] deal).
Oh! Apparently, /puel/ means 'east'! That explains where "Puelche" comes from, as the Puelche live east of the Andes.
And that concludes today's lesson.