"deü" meaning in Ancien français

{
  "categories": [
    {
      "kind": "other",
      "name": "Formes de verbes en ancien français",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Ancien français",
      "orig": "ancien français",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Ancien français",
  "lang_code": "fro",
  "pos": "verb",
  "pos_title": "Forme de verbe",
  "senses": [
    {
      "form_of": [
        {
          "word": "devoir"
        }
      ],
      "glosses": [
        "Variante, dans les éditions modernes, de deu. Participe passé de devoir."
      ],
      "id": "fr-deü-fro-verb-oWsvlh3i"
    }
  ],
  "tags": [
    "form-of"
  ],
  "word": "deü"
}

{
  "categories": [
    "Formes de verbes en ancien français",
    "ancien français"
  ],
  "lang": "Ancien français",
  "lang_code": "fro",
  "pos": "verb",
  "pos_title": "Forme de verbe",
  "senses": [
    {
      "form_of": [
        {
          "word": "devoir"
        }
      ],
      "glosses": [
        "Variante, dans les éditions modernes, de deu. Participe passé de devoir."
      ]
    }
  ],
  "tags": [
    "form-of"
  ],
  "word": "deü"
}