@mhka it sorta works when you have Cache in a model name and use relation but not quite :)
@mulander One cach, two cache.
Where's the problem? 
@Nihl it takes the magic away :(
@mulander a backwards compatibility requirement at this point https://github.com/rails/rails/blob/34d1e5d04d2e2583bf28fc2365f43d5917e2c648/activesupport/lib/active_support/inflector/methods.rb#L6-L9
@bonzoesc they could ship a default inflection (config/initializers/inflections.rb) for the broken ones - that would at least fix all newly created projects.
@mulander until they have to interop with an old app
english pluralization isn't one-to-one/injective so whatever
@mulander random guess: a misspelling cache, which returns sorta the right thing but not quite?