Hanks did not say it, It was a dude in mission control when the team constructed the fix for the CO2 problem.

"“Among the men in the Canaveral blockhouse and the Houston control room, there was no greater tribute a controller could be paid than to describe him, in the rough poetry of the rocket community, as a “steely-eyed missile man.” There weren’t many steely-eyed missile men in the NASA family. [Wernher] Von Braun was certainly one, [Chris] Kraft was certainly one, [Gene] Kranz was probably one too.”

It does not seem to originate with Lovall, but he talks about it in his memoir.

Edit:- I did not know it had real roots so thanks for that detail.

Hanks did not say it, It was a dude in mission control when the team constructed the fix for the CO2 problem.

"“Among the men in the Canaveral blockhouse and the Houston control room, there was no greater tribute a controller could be paid than to describe him, in the rough poetry of the rocket community, as a “steely-eyed missile man.” There weren’t many steely-eyed missile men in the NASA family. [Wernher] Von Braun was certainly one, [Chris] Kraft was certainly one, [Gene] Kranz was probably one too.”

It does not seem to originate with Lovall, but he talks about it in his memoir.