"fidejussissem" meaning in Latin

{
  "forms": [
    {
      "form": "fidējussissem",
      "tags": [
        "canonical"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "la",
        "2": "verb form",
        "head": "fidējussissem"
      },
      "expansion": "fidējussissem",
      "name": "head"
    }
  ],
  "lang": "Latin",
  "lang_code": "la",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Latin entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "form_of": [
        {
          "word": "fidējubeō"
        }
      ],
      "glosses": [
        "first-person singular pluperfect active subjunctive of fidējubeō"
      ],
      "id": "en-fidejussissem-la-verb-BYqc3QWT",
      "links": [
        [
          "fidējubeō",
          "fidejubeo#Latin"
        ]
      ],
      "tags": [
        "active",
        "first-person",
        "form-of",
        "pluperfect",
        "singular",
        "subjunctive"
      ]
    }
  ],
  "word": "fidejussissem"
}

{
  "forms": [
    {
      "form": "fidējussissem",
      "tags": [
        "canonical"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "la",
        "2": "verb form",
        "head": "fidējussissem"
      },
      "expansion": "fidējussissem",
      "name": "head"
    }
  ],
  "lang": "Latin",
  "lang_code": "la",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "Latin entries with incorrect language header",
        "Latin non-lemma forms",
        "Latin terms spelled with J",
        "Latin verb forms",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "form_of": [
        {
          "word": "fidējubeō"
        }
      ],
      "glosses": [
        "first-person singular pluperfect active subjunctive of fidējubeō"
      ],
      "links": [
        [
          "fidējubeō",
          "fidejubeo#Latin"
        ]
      ],
      "tags": [
        "active",
        "first-person",
        "form-of",
        "pluperfect",
        "singular",
        "subjunctive"
      ]
    }
  ],
  "word": "fidejussissem"
}