In English it is an archaic spelling of treasure. It means "safe" or "vault" in German.
► uses
Uses:
Napoleon, too, carried away his own personal tresor, but on seeing the baggage trains that impeded the army, he was (Thiers says) horror-struck.
Leo Tolstoy. War and Peace: 13 (Book Thirteen)
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This gære for the King Stephan ofer sæ to Normandi; and ther wes under fangen, forthi thæt hi wenden thæt he sculde ben alsuic alse the eom wæs, and for he hadde get his tresor; ac he todeld it and scatered sotlice.