Drake

Nice find. I think the English rule is that in this case if the che follows a vowel it will be 'sh'. Like Douche is doosh because the che is followed by 'U' which is a vowel.

It's not the case in avalanche and psyche. Remember 'Y' is sometimes a vowel (a,e,i,o,u, and sometimes y). In this case I don't think the 'y' is considered a voewel. Nor is N a vowel. And that's why they're pronounced differently. Psyche sounds like Sike and Avalanche sounds like avalanch.