She took her letters ( which had been carefully saved by the Moore children ) and chose a letter written on 4 September 1893 to five-year-old Noel about a rabbit named Peter . Potter embraced the suggestion , and , borrowing her complete correspondence ( which had been carefully preserved by the Moore children ) , selected a letter written on 4 September 1893 to five-year-old Noel that featured a tale about a rabbit named Peter .