from Wiktionary, Creative Commons Attribution/Share-Alike License
- interj. Used in Remembrance Day ceremonies as a caution against forgetting those who died in war.
- interj. Used on ANZAC Day memorials in remembrance of those who fell in the First World War
From Rudyard Kipling′s 1897 poem Recessional. (Wiktionary)
Trace as espionage jargon surely was adapted from similar usages in the wider world: skip trace, or lest we forget Mr. Keene, tracer of lost persons.