Laudator Temporis Acti

William Bryant Logan, Oak: The Frame of Civilization (New York: W.W. Norton & Company, 2005), p. 253:

Six months later, the Union ironclad went down on New Year's Eve in a storm off the North Carolina banks. Though "impregnable" enough, she was not very seaworthy. She left us with one battle and her name, conceived by her engineer creator: Monitor, which in Greek means "the warning."

Monitor is Latin, not Greek, and it means "one who reminds or warns," not "warning." Greek words meaning "warning" include νουθέτημα (nouthétēma) and νουθέτησις (nouthétēsis).

The "engineer creator" of the Monitor was John Ericsson, who wrote in a Jan. 20, 1862, letter to Assistant Secretary of the Navy Gustavus V. Fox:

In accordance with your request, I now submit for your approbation a name for the floating battery at Greenpoint. The impregnable and aggressive character of this structure will admonish the leaders of the Southern rebellion that the batteries on the banks of their rivers will no longer present barriers to the entrance of the Union forces. The iron-clad intruder will provide a severe monitor to those leaders. But there are other leaders who will also be startled and admonished by the booming of the guns from the impregnable iron turret. 'Downing Street' will hardly view with indifference this last 'Yankee notion' — this monitor. To the Lords of the Admiralty the new craft will be a monitor, suggesting doubts as to the propriety of completing those four steel ships at $3,500,000 apiece. On these and many similar grounds I propose to name the new battery Monitor.