"rock alum" meaning in English

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    {
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        "2": "roche",
        "3": "",
        "4": "rock"
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      "expansion": "French roche (“rock”)",
      "name": "cog"
    }
  ],
  "etymology_text": "Probably by confusion with French roche (“rock”).",
  "head_templates": [
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      "args": {
        "1": "?"
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      "expansion": "rock alum",
      "name": "en-noun"
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
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        {
          "word": "roche alum"
        }
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          "source": "w"
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      "glosses": [
        "Alternative form of roche alum"
      ],
      "id": "en-rock_alum-en-noun-SeLVZqX0",
      "links": [
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      "tags": [
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    }
  ],
  "word": "rock alum"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "fr",
        "2": "roche",
        "3": "",
        "4": "rock"
      },
      "expansion": "French roche (“rock”)",
      "name": "cog"
    }
  ],
  "etymology_text": "Probably by confusion with French roche (“rock”).",
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "rock alum",
      "name": "en-noun"
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "roche alum"
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        "English nouns",
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      ],
      "glosses": [
        "Alternative form of roche alum"
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  "word": "rock alum"
}