"proto-Britain" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "proto-Britain",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "2018, Tim Flannery, Europe: A Natural History, page 55:",
          "text": "There were still plenty of islands about, including proto-Britain in the west and Iberia in the south[.]",
          "type": "quote"
        }
      ],
      "glosses": [
        "The formations far back in geological time that resulted eventually in the British Isles."
      ],
      "id": "en-proto-Britain-en-noun-X~0x1TOB"
    }
  ],
  "word": "proto-Britain"
}

{
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "proto-Britain",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English nouns with unknown or uncertain plurals",
        "English terms with quotations",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "ref": "2018, Tim Flannery, Europe: A Natural History, page 55:",
          "text": "There were still plenty of islands about, including proto-Britain in the west and Iberia in the south[.]",
          "type": "quote"
        }
      ],
      "glosses": [
        "The formations far back in geological time that resulted eventually in the British Isles."
      ]
    }
  ],
  "word": "proto-Britain"
}