"light a fire under" meaning in English

{
  "etymology_text": "Referring to a time when, if chimney sweeps were afraid to ascend a chimney, the fire would be lit under them in order to motivate them to climb to the top.",
  "forms": [
    {
      "form": "lights a fire under",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "lighting a fire under",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "lit a fire under",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "lit a fire under",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "light<,,lit> a fire under"
      },
      "expansion": "light a fire under (third-person singular simple present lights a fire under, present participle lighting a fire under, simple past and past participle lit a fire under)",
      "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": "Let me see if I can light a fire under the waiter to get our order sooner."
        }
      ],
      "glosses": [
        "To motivate or encourage (someone) to start sooner or move faster."
      ],
      "id": "en-light_a_fire_under-en-verb-7vrGwxH-",
      "links": [
        [
          "motivate",
          "motivate"
        ]
      ],
      "raw_glosses": [
        "(idiomatic, transitive) To motivate or encourage (someone) to start sooner or move faster."
      ],
      "tags": [
        "idiomatic",
        "transitive"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-light a fire under.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/7/72/En-au-light_a_fire_under.ogg/En-au-light_a_fire_under.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/7/72/En-au-light_a_fire_under.ogg",
      "tags": [
        "Australia"
      ],
      "text": "Audio (AU)"
    }
  ],
  "word": "light a fire under"
}

{
  "etymology_text": "Referring to a time when, if chimney sweeps were afraid to ascend a chimney, the fire would be lit under them in order to motivate them to climb to the top.",
  "forms": [
    {
      "form": "lights a fire under",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "lighting a fire under",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "lit a fire under",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "lit a fire under",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "light<,,lit> a fire under"
      },
      "expansion": "light a fire under (third-person singular simple present lights a fire under, present participle lighting a fire under, simple past and past participle lit a fire under)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English idioms",
        "English lemmas",
        "English multiword terms",
        "English terms with audio links",
        "English transitive verbs",
        "English verbs"
      ],
      "examples": [
        {
          "text": "Let me see if I can light a fire under the waiter to get our order sooner."
        }
      ],
      "glosses": [
        "To motivate or encourage (someone) to start sooner or move faster."
      ],
      "links": [
        [
          "motivate",
          "motivate"
        ]
      ],
      "raw_glosses": [
        "(idiomatic, transitive) To motivate or encourage (someone) to start sooner or move faster."
      ],
      "tags": [
        "idiomatic",
        "transitive"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-light a fire under.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/7/72/En-au-light_a_fire_under.ogg/En-au-light_a_fire_under.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/7/72/En-au-light_a_fire_under.ogg",
      "tags": [
        "Australia"
      ],
      "text": "Audio (AU)"
    }
  ],
  "word": "light a fire under"
}