"elf king" meaning in English

{
  "forms": [
    {
      "form": "elf kings",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "elf king (plural elf kings)",
      "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"
        }
      ],
      "examples": [
        {
          "ref": "1828, Thomas Keightley, The Fairy Mythology, volume I, London: William Harrison Ainsworth, page 137",
          "text": "There is also a tune called the Elf-king's tune, which several of the good fiddlers know right well, but never venture to play, for as soon as it begins, both old and young, and even inanimate objects, are impelled to dance, and the player cannot stop unless he can play the air backwards, or that some one comes behind him and cuts the strings of his fiddle.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A male monarch of elves."
      ],
      "id": "en-elf_king-en-noun-YMCQEQK6",
      "synonyms": [
        {
          "word": "elf-king"
        }
      ]
    }
  ],
  "word": "elf king"
}

{
  "forms": [
    {
      "form": "elf kings",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "elf king (plural elf kings)",
      "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 terms with quotations"
      ],
      "examples": [
        {
          "ref": "1828, Thomas Keightley, The Fairy Mythology, volume I, London: William Harrison Ainsworth, page 137",
          "text": "There is also a tune called the Elf-king's tune, which several of the good fiddlers know right well, but never venture to play, for as soon as it begins, both old and young, and even inanimate objects, are impelled to dance, and the player cannot stop unless he can play the air backwards, or that some one comes behind him and cuts the strings of his fiddle.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A male monarch of elves."
      ]
    }
  ],
  "synonyms": [
    {
      "word": "elf-king"
    }
  ],
  "word": "elf king"
}