"terminus a quo" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "la",
        "3": "terminus a quo"
      },
      "expansion": "Latin terminus a quo",
      "name": "bor"
    }
  ],
  "etymology_text": "Borrowed from Latin terminus a quo (literally, \"the limit from which\").",
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "terminus a quo",
      "name": "en-noun"
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
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          "source": "w"
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        },
        {
          "kind": "other",
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        }
      ],
      "glosses": [
        "The lower limit of dating, as of the earliest plausible date at which a fact could have occurred or a document could have been written."
      ],
      "id": "en-terminus_a_quo-en-noun-QfvL0Tgr",
      "related": [
        {
          "word": "terminus"
        },
        {
          "word": "terminus ante quem"
        },
        {
          "word": "terminus ad quem"
        }
      ]
    }
  ],
  "word": "terminus a quo"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "la",
        "3": "terminus a quo"
      },
      "expansion": "Latin terminus a quo",
      "name": "bor"
    }
  ],
  "etymology_text": "Borrowed from Latin terminus a quo (literally, \"the limit from which\").",
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "terminus a quo",
      "name": "en-noun"
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "terminus"
    },
    {
      "word": "terminus ante quem"
    },
    {
      "word": "terminus ad quem"
    }
  ],
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English nouns with unknown or uncertain plurals",
        "English terms borrowed from Latin",
        "English terms derived from Latin",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "The lower limit of dating, as of the earliest plausible date at which a fact could have occurred or a document could have been written."
      ]
    }
  ],
  "word": "terminus a quo"
}