Mdwrite wants to use the "metadata" keychain: what is this?

Just got this for the first time today while setting a label on a file. Not sure what the password for the metadata keychain is, but it's clearly not meant to be modified.

The contents seem to be some kind of encryption key for Spotlight, so at a guess I'd say it must encrypt metadata for files, presumably to prevent users or unauthorised applications from viewing the contents of any metadata indexes that Spotlight generates for use when searching, possibly to prevent harvesting of data or even personal details from within Spotlight indexes?

It seems like a good thing to me, the error likely stems from the keychain somehow becoming locked when it's not supposed to be, which may prevent Spotlight from being able to index files until you logout and back in, or restart, but I haven't done any kind of test to find out, just trying to make an educated guess at the whole thing =)

Same here. Admin password did not work.

I got it after i did a whole recovery form a Time Machine Backup.

No idea what triggered this pop-up.

The password is metadata