"-dd" meaning in Swedish

{
  "head_templates": [
    {
      "args": {
        "1": "sv",
        "2": "suffixes"
      },
      "expansion": "-dd",
      "name": "head"
    }
  ],
  "lang": "Swedish",
  "lang_code": "sv",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with raw sortkeys",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Swedish entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Swedish entries with language name categories using raw markup",
          "parents": [
            "Entries with language name categories using raw markup",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Swedish terms with redundant sortkeys",
          "parents": [
            "Terms with redundant sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A suffix that forms the past participle of certain verbs (the third conjugation, verbs that have infinitives without -a)."
      ],
      "id": "en--dd-sv-suffix-3mUZjx0C",
      "links": [
        [
          "-a",
          "-a"
        ]
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "word": "-dd"
}

{
  "head_templates": [
    {
      "args": {
        "1": "sv",
        "2": "suffixes"
      },
      "expansion": "-dd",
      "name": "head"
    }
  ],
  "lang": "Swedish",
  "lang_code": "sv",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        "Pages with raw sortkeys",
        "Swedish entries with incorrect language header",
        "Swedish entries with language name categories using raw markup",
        "Swedish lemmas",
        "Swedish suffixes",
        "Swedish terms with redundant sortkeys"
      ],
      "glosses": [
        "A suffix that forms the past participle of certain verbs (the third conjugation, verbs that have infinitives without -a)."
      ],
      "links": [
        [
          "-a",
          "-a"
        ]
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "word": "-dd"
}