index_ prefix to path erroneously added to rails 4 route

index_ prefix to path erroneously added to rails 4 route

I added a controller "Triage" to my application, and added a put route as
follows:
resources :triage do
collection do
put :process_multiple
end
end
Instead of the expected process_multiple_triage_path route, it seems it is
processed as process_multiple_triage_index_path:
process_multiple_triage_index_path PUT /triage/process_multiple(.:format)
triage#process_multiple triage_index_path GET /triage(.:format)
triage#index POST /triage(.:format) triage#create
I can't seem to figure out why the index_ "prefix" is being added.