"Afon Merswy" meaning in Welsh

{
  "etymology_templates": [
    {
      "args": {
        "1": "cy",
        "2": "ang",
        "3": "Mæres ēa",
        "4": "",
        "5": "boundary river"
      },
      "expansion": "Old English Mæres ēa (“boundary river”)",
      "name": "der"
    }
  ],
  "etymology_text": "Old English Mæres ēa (“boundary river”).",
  "head_templates": [
    {
      "args": {
        "1": "f",
        "head": "Afon Merswy"
      },
      "expansion": "Afon Merswy f",
      "name": "cy-proper noun"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "name",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Welsh entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "place",
          "langcode": "cy",
          "name": "Places in England",
          "orig": "cy:Places in England",
          "parents": [
            "Places",
            "Names",
            "All topics",
            "Proper nouns",
            "Terms by semantic function",
            "Fundamental",
            "Nouns",
            "Lemmas"
          ],
          "source": "w"
        },
        {
          "kind": "place",
          "langcode": "cy",
          "name": "Rivers in England",
          "orig": "cy:Rivers in England",
          "parents": [
            "Rivers",
            "Places",
            "Bodies of water",
            "Names",
            "Landforms",
            "Water",
            "All topics",
            "Proper nouns",
            "Terms by semantic function",
            "Earth",
            "Liquids",
            "Fundamental",
            "Nouns",
            "Nature",
            "Matter",
            "Lemmas",
            "Chemistry",
            "Sciences"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "the River Mersey (a river in England)"
      ],
      "id": "en-Afon_Merswy-cy-name-A20yH2rS",
      "links": [
        [
          "Mersey",
          "Mersey#English"
        ],
        [
          "England",
          "England#English"
        ]
      ],
      "related": [
        {
          "tags": [
            "Merseyside"
          ],
          "word": "Glannau Merswy"
        }
      ],
      "tags": [
        "feminine"
      ]
    }
  ],
  "word": "Afon Merswy"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "cy",
        "2": "ang",
        "3": "Mæres ēa",
        "4": "",
        "5": "boundary river"
      },
      "expansion": "Old English Mæres ēa (“boundary river”)",
      "name": "der"
    }
  ],
  "etymology_text": "Old English Mæres ēa (“boundary river”).",
  "head_templates": [
    {
      "args": {
        "1": "f",
        "head": "Afon Merswy"
      },
      "expansion": "Afon Merswy f",
      "name": "cy-proper noun"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "name",
  "related": [
    {
      "tags": [
        "Merseyside"
      ],
      "word": "Glannau Merswy"
    }
  ],
  "senses": [
    {
      "categories": [
        "Welsh entries with incorrect language header",
        "Welsh feminine nouns",
        "Welsh lemmas",
        "Welsh multiword terms",
        "Welsh proper nouns",
        "Welsh terms derived from Old English",
        "cy:Places in England",
        "cy:Rivers in England"
      ],
      "glosses": [
        "the River Mersey (a river in England)"
      ],
      "links": [
        [
          "Mersey",
          "Mersey#English"
        ],
        [
          "England",
          "England#English"
        ]
      ],
      "tags": [
        "feminine"
      ]
    }
  ],
  "word": "Afon Merswy"
}