Story highlights Comey was asked about his decision to go public with his Clinton investigation conclusions

Comey was testifying about the Russia investigation

Washington (CNN) Former FBI Director James Comey said Thursday that former Attorney General Loretta Lynch requested he call the Clinton investigation a "matter," partially leading to his decision to make his now-famous statement about the results of that investigation.

Comey said what "capped" his decision to make his public remarks about the conclusion was a publicly reported meeting by Lynch and former President Bill Clinton as their planes were on the same tarmac. He said he decided he had to "protect the credibility of the investigation."

That was public knowledge and drew criticism at the time, but Comey also revealed that Lynch had previously given him instructions on the investigation into the use of a private server by former Secretary of State Hillary Clinton -- which "concerned" him.

"At one point, the attorney general had directed me not to call it an investigation but instead to call it a matter, which confused me and concerned me," Comey said. "That was one of the bricks in the load that led me to conclude I have to step away from the department if we're to close this case credibly."

He later explained that it felt "silly" to not acknowledge the investigation publicly as both presidential campaigns were speaking publicly about it -- but said the Clinton campaign was using "euphemisms" for it, including a "matter."