"know someone when" meaning in English

{
  "etymology_text": "From the formulaic phrase by which speakers begin reminiscence of now-famous persons.",
  "forms": [
    {
      "form": "knows someone when",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "knowing someone when",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "knew someone when",
      "tags": [
        "past"
      ]
    },
    {
      "form": "known someone when",
      "tags": [
        "participle",
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "know<,,knew,known> someone when"
      },
      "expansion": "know someone when (third-person singular simple present knows someone when, present participle knowing someone when, simple past knew someone when, past participle known someone when)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "1915, \"Interesting People: Charles Bullard: A Famous Photographer of Cats\", in \"The American Magazine\"\nHis friends thought him crazy, as friends always think when a man has an original idea and acts on it. Now, when his friends speak of him they invariably add, \"I knew him when—\""
        },
        {
          "ref": "1918, Western Electric News",
          "text": "Of course when your school chum comes in from the old home town you want to send him back a life-long member of the \"I-knew-him-when Club.\" You picture him back home, just a wee bit superior, as befits a friend of the great, holding forth to the boy's at the Sunshine Athletic Club.",
          "type": "quotation"
        },
        {
          "text": "1920, George Ade, I Knew Him When--: A Hoosier Fable Dealing with the Happy Days of Away Back Yonder:",
          "type": "quotation"
        },
        {
          "ref": "1971, W. A. Mambert, The Elements of Effective Communication: Idea, Power, Tactics, page 146",
          "text": "The classical example of this is the \"I knew him when\" syndrome. Consider your immediate family. They know you as you really are, if anyone does.",
          "type": "quotation"
        },
        {
          "ref": "2008, Lisa Tucker, The Cure for Modern Life, page 89",
          "text": "\"Well, congratulations. On the speech, everything.\" She stood up straighter and forced a smile. \"I can always say I knew him when.\"",
          "type": "quotation"
        }
      ],
      "glosses": [
        "To have known a famous person before he or she was famous."
      ],
      "id": "en-know_someone_when-en-verb-11wryCk0",
      "links": [
        [
          "famous",
          "famous"
        ]
      ],
      "raw_glosses": [
        "(usually in the past tense) To have known a famous person before he or she was famous."
      ],
      "tags": [
        "past",
        "usually"
      ]
    }
  ],
  "word": "know someone when"
}

{
  "etymology_text": "From the formulaic phrase by which speakers begin reminiscence of now-famous persons.",
  "forms": [
    {
      "form": "knows someone when",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "knowing someone when",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "knew someone when",
      "tags": [
        "past"
      ]
    },
    {
      "form": "known someone when",
      "tags": [
        "participle",
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "know<,,knew,known> someone when"
      },
      "expansion": "know someone when (third-person singular simple present knows someone when, present participle knowing someone when, simple past knew someone when, past participle known someone when)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English terms with quotations",
        "English verbs",
        "Quotation templates to be cleaned"
      ],
      "examples": [
        {
          "text": "1915, \"Interesting People: Charles Bullard: A Famous Photographer of Cats\", in \"The American Magazine\"\nHis friends thought him crazy, as friends always think when a man has an original idea and acts on it. Now, when his friends speak of him they invariably add, \"I knew him when—\""
        },
        {
          "ref": "1918, Western Electric News",
          "text": "Of course when your school chum comes in from the old home town you want to send him back a life-long member of the \"I-knew-him-when Club.\" You picture him back home, just a wee bit superior, as befits a friend of the great, holding forth to the boy's at the Sunshine Athletic Club.",
          "type": "quotation"
        },
        {
          "text": "1920, George Ade, I Knew Him When--: A Hoosier Fable Dealing with the Happy Days of Away Back Yonder:",
          "type": "quotation"
        },
        {
          "ref": "1971, W. A. Mambert, The Elements of Effective Communication: Idea, Power, Tactics, page 146",
          "text": "The classical example of this is the \"I knew him when\" syndrome. Consider your immediate family. They know you as you really are, if anyone does.",
          "type": "quotation"
        },
        {
          "ref": "2008, Lisa Tucker, The Cure for Modern Life, page 89",
          "text": "\"Well, congratulations. On the speech, everything.\" She stood up straighter and forced a smile. \"I can always say I knew him when.\"",
          "type": "quotation"
        }
      ],
      "glosses": [
        "To have known a famous person before he or she was famous."
      ],
      "links": [
        [
          "famous",
          "famous"
        ]
      ],
      "raw_glosses": [
        "(usually in the past tense) To have known a famous person before he or she was famous."
      ],
      "tags": [
        "past",
        "usually"
      ]
    }
  ],
  "word": "know someone when"
}