"yffach" meaning in Welsh

{
  "etymology_text": "Alteration of uffern.",
  "head_templates": [
    {
      "args": {
        "1": "cy",
        "2": "interjection"
      },
      "expansion": "yffach",
      "name": "head"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "intj",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "hell, damn",
          "word": "uffern"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Welsh entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "derived": [
        {
          "word": "yffach o"
        }
      ],
      "examples": [
        {
          "english": "Damn! Do you have to pray so much?",
          "text": "Yffach! O's rhaid i ti weddi gymaint?",
          "type": "example"
        }
      ],
      "glosses": [
        "Alternative form of uffern (“hell, damn”)"
      ],
      "id": "en-yffach-cy-intj-p8Nv60GS",
      "links": [
        [
          "uffern",
          "uffern#Welsh"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈəfaχ/"
    }
  ],
  "word": "yffach"
}

{
  "derived": [
    {
      "word": "yffach o"
    }
  ],
  "etymology_text": "Alteration of uffern.",
  "head_templates": [
    {
      "args": {
        "1": "cy",
        "2": "interjection"
      },
      "expansion": "yffach",
      "name": "head"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "intj",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "hell, damn",
          "word": "uffern"
        }
      ],
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Welsh entries with incorrect language header",
        "Welsh interjections",
        "Welsh lemmas",
        "Welsh terms with usage examples"
      ],
      "examples": [
        {
          "english": "Damn! Do you have to pray so much?",
          "text": "Yffach! O's rhaid i ti weddi gymaint?",
          "type": "example"
        }
      ],
      "glosses": [
        "Alternative form of uffern (“hell, damn”)"
      ],
      "links": [
        [
          "uffern",
          "uffern#Welsh"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈəfaχ/"
    }
  ],
  "word": "yffach"
}