"ef" meaning in Icelandic

{
  "etymology_templates": [
    {
      "args": {
        "1": "is",
        "2": "non",
        "3": "ef"
      },
      "expansion": "Old Norse ef",
      "name": "der"
    },
    {
      "args": {
        "1": "is",
        "2": "gem-pro",
        "3": "*jabai"
      },
      "expansion": "Proto-Germanic *jabai",
      "name": "der"
    }
  ],
  "etymology_text": "From Old Norse ef, from Proto-Germanic *jabai.",
  "head_templates": [
    {
      "args": {
        "1": "is",
        "2": "conjunction"
      },
      "expansion": "ef",
      "name": "head"
    }
  ],
  "lang": "Icelandic",
  "lang_code": "is",
  "pos": "conj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Icelandic entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 13 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "if"
      ],
      "id": "en-ef-is-conj-k19oMZ1P",
      "links": [
        [
          "if",
          "if#Icelandic"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɛːv/"
    },
    {
      "rhymes": "-ɛːv"
    }
  ],
  "word": "ef"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "is",
        "2": "non",
        "3": "ef"
      },
      "expansion": "Old Norse ef",
      "name": "der"
    },
    {
      "args": {
        "1": "is",
        "2": "gem-pro",
        "3": "*jabai"
      },
      "expansion": "Proto-Germanic *jabai",
      "name": "der"
    }
  ],
  "etymology_text": "From Old Norse ef, from Proto-Germanic *jabai.",
  "head_templates": [
    {
      "args": {
        "1": "is",
        "2": "conjunction"
      },
      "expansion": "ef",
      "name": "head"
    }
  ],
  "lang": "Icelandic",
  "lang_code": "is",
  "pos": "conj",
  "senses": [
    {
      "categories": [
        "Icelandic conjunctions",
        "Icelandic entries with incorrect language header",
        "Icelandic lemmas",
        "Icelandic terms derived from Old Norse",
        "Icelandic terms derived from Proto-Germanic",
        "Pages with 13 entries",
        "Pages with entries",
        "Rhymes:Icelandic/ɛːv",
        "Rhymes:Icelandic/ɛːv/1 syllable"
      ],
      "glosses": [
        "if"
      ],
      "links": [
        [
          "if",
          "if#Icelandic"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɛːv/"
    },
    {
      "rhymes": "-ɛːv"
    }
  ],
  "word": "ef"
}