"many happy returns" meaning in English

{
  "etymology_text": "The earliest attributable use was by Lady Newdigate in a letter written in 1789 (and published in Newdigate-Newdegate Cheverels in 1898): Many happy returns of ye day to us my Dr Love.",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "noun",
        "head": "many happy returns"
      },
      "expansion": "many happy returns",
      "name": "head"
    }
  ],
  "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"
        }
      ],
      "glosses": [
        "A greeting, usually for birthdays, in reference to the passing year; Happy birthday!"
      ],
      "id": "en-many_happy_returns-en-noun-kOeDeugi",
      "links": [
        [
          "greeting",
          "greeting#English"
        ],
        [
          "birthdays",
          "birthdays#English"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) A greeting, usually for birthdays, in reference to the passing year; Happy birthday!"
      ],
      "tags": [
        "idiomatic"
      ],
      "translations": [
        {
          "code": "fi",
          "lang": "Finnish",
          "sense": "Many happy returns!",
          "word": "paljon onnea"
        },
        {
          "code": "el",
          "lang": "Greek",
          "roman": "chrónia pollá",
          "sense": "Many happy returns!",
          "tags": [
            "masculine",
            "plural"
          ],
          "word": "χρόνια πολλά"
        },
        {
          "code": "hu",
          "lang": "Hungarian",
          "roman": "informal; the formal variant is with éltesse",
          "sense": "Many happy returns!",
          "word": "Isten éltessen! (sokáig)"
        },
        {
          "code": "lv",
          "lang": "Latvian",
          "sense": "Many happy returns!",
          "word": "daudz baltu dieniņu"
        },
        {
          "code": "gv",
          "lang": "Manx",
          "sense": "Many happy returns!",
          "word": "laa ruggyree sonney dhyt"
        },
        {
          "code": "pl",
          "lang": "Polish",
          "sense": "Many happy returns!",
          "word": "sto lat"
        },
        {
          "code": "ro",
          "lang": "Romanian",
          "sense": "Many happy returns!",
          "word": "mulți ani înainte"
        },
        {
          "code": "ru",
          "lang": "Russian",
          "roman": "dolgix let žizni",
          "sense": "Many happy returns!",
          "word": "долгих лет жизни"
        }
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-many happy returns.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/8/89/En-au-many_happy_returns.ogg/En-au-many_happy_returns.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/8/89/En-au-many_happy_returns.ogg",
      "tags": [
        "Australia"
      ],
      "text": "Audio (AU)"
    }
  ],
  "word": "many happy returns"
}

{
  "etymology_text": "The earliest attributable use was by Lady Newdigate in a letter written in 1789 (and published in Newdigate-Newdegate Cheverels in 1898): Many happy returns of ye day to us my Dr Love.",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "noun",
        "head": "many happy returns"
      },
      "expansion": "many happy returns",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English idioms",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with audio links"
      ],
      "glosses": [
        "A greeting, usually for birthdays, in reference to the passing year; Happy birthday!"
      ],
      "links": [
        [
          "greeting",
          "greeting#English"
        ],
        [
          "birthdays",
          "birthdays#English"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) A greeting, usually for birthdays, in reference to the passing year; Happy birthday!"
      ],
      "tags": [
        "idiomatic"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-many happy returns.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/8/89/En-au-many_happy_returns.ogg/En-au-many_happy_returns.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/8/89/En-au-many_happy_returns.ogg",
      "tags": [
        "Australia"
      ],
      "text": "Audio (AU)"
    }
  ],
  "translations": [
    {
      "code": "fi",
      "lang": "Finnish",
      "sense": "Many happy returns!",
      "word": "paljon onnea"
    },
    {
      "code": "el",
      "lang": "Greek",
      "roman": "chrónia pollá",
      "sense": "Many happy returns!",
      "tags": [
        "masculine",
        "plural"
      ],
      "word": "χρόνια πολλά"
    },
    {
      "code": "hu",
      "lang": "Hungarian",
      "roman": "informal; the formal variant is with éltesse",
      "sense": "Many happy returns!",
      "word": "Isten éltessen! (sokáig)"
    },
    {
      "code": "lv",
      "lang": "Latvian",
      "sense": "Many happy returns!",
      "word": "daudz baltu dieniņu"
    },
    {
      "code": "gv",
      "lang": "Manx",
      "sense": "Many happy returns!",
      "word": "laa ruggyree sonney dhyt"
    },
    {
      "code": "pl",
      "lang": "Polish",
      "sense": "Many happy returns!",
      "word": "sto lat"
    },
    {
      "code": "ro",
      "lang": "Romanian",
      "sense": "Many happy returns!",
      "word": "mulți ani înainte"
    },
    {
      "code": "ru",
      "lang": "Russian",
      "roman": "dolgix let žizni",
      "sense": "Many happy returns!",
      "word": "долгих лет жизни"
    }
  ],
  "word": "many happy returns"
}