"í milli" meaning in Old Norse

{
  "etymology_templates": [
    {
      "args": {
        "1": "non",
        "2": "gem-pro",
        "3": "*midlą"
      },
      "expansion": "Proto-Germanic *midlą",
      "name": "der"
    },
    {
      "args": {
        "1": "en",
        "2": "middle"
      },
      "expansion": "English middle",
      "name": "cog"
    }
  ],
  "etymology_text": "From earlier í miðli, originally dative of Proto-Germanic *midlą, related to meðal, English middle.",
  "head_templates": [
    {
      "args": {
        "1": "non",
        "2": "preposition"
      },
      "expansion": "í milli",
      "name": "head"
    }
  ],
  "lang": "Old Norse",
  "lang_code": "non",
  "pos": "prep",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Old Norse entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Old Norse prepositions",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "in between"
      ],
      "id": "en-í_milli-non-prep-RUeyPHNB",
      "links": [
        [
          "in between",
          "in between"
        ]
      ],
      "raw_glosses": [
        "(with genitive) in between"
      ],
      "synonyms": [
        {
          "word": "á milli"
        },
        {
          "word": "á millu"
        },
        {
          "word": "ímillum"
        },
        {
          "word": "í millum"
        }
      ],
      "tags": [
        "with-genitive"
      ]
    }
  ],
  "word": "í milli"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "non",
        "2": "gem-pro",
        "3": "*midlą"
      },
      "expansion": "Proto-Germanic *midlą",
      "name": "der"
    },
    {
      "args": {
        "1": "en",
        "2": "middle"
      },
      "expansion": "English middle",
      "name": "cog"
    }
  ],
  "etymology_text": "From earlier í miðli, originally dative of Proto-Germanic *midlą, related to meðal, English middle.",
  "head_templates": [
    {
      "args": {
        "1": "non",
        "2": "preposition"
      },
      "expansion": "í milli",
      "name": "head"
    }
  ],
  "lang": "Old Norse",
  "lang_code": "non",
  "pos": "prep",
  "senses": [
    {
      "categories": [
        "Old Norse entries with incorrect language header",
        "Old Norse lemmas",
        "Old Norse multiword terms",
        "Old Norse prepositions",
        "Old Norse terms derived from Proto-Germanic"
      ],
      "glosses": [
        "in between"
      ],
      "links": [
        [
          "in between",
          "in between"
        ]
      ],
      "raw_glosses": [
        "(with genitive) in between"
      ],
      "tags": [
        "with-genitive"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "á milli"
    },
    {
      "word": "á millu"
    },
    {
      "word": "ímillum"
    },
    {
      "word": "í millum"
    }
  ],
  "word": "í milli"
}