This is from 2014 and likely not a Google hack or leak but a subset of credentials revealed by hacks or leaks from other sites.

https://productforums.google.com/forum/#!topic/gmail/4q3AYMi... and https://facepunch.com/showthread.php?t=1423764 refer to this link.

Edit to add: https://haveibeenpwned.com/PwnedWebsites#BTSec