This doesn't seem to appear in the current web site messages? As far as I know we've never used camelCase for message identifiers?
This message is defined and is used in Potlatch2.
- Main-oauth.tryAccessButton ("Try access")
Ah well I'm not really the right person to ask about PL2 stuff, but as best I can tell from the source it is a label that appears on an action button used to test if OAuth access to the API is working.