"калъ" meaning in Vieux slave

{
  "categories": [
    {
      "kind": "other",
      "name": "Mots en vieux slave issus d’un mot en indo-européen commun",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Noms communs en vieux slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Vieux slave",
      "orig": "vieux slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Étymologies en vieux slave incluant une reconstruction",
      "parents": [],
      "source": "w"
    }
  ],
  "derived": [
    {
      "lang": "Bulgare",
      "lang_code": "bg",
      "word": "кал"
    },
    {
      "lang": "Polonais",
      "lang_code": "pl",
      "word": "kał"
    },
    {
      "lang": "Tchèque",
      "lang_code": "cs",
      "word": "kal"
    }
  ],
  "etymology_texts": [
    "De l'indo-européen commun *kwal- qui donne le grec ancien πηλός, pêlós (« boue »), le lituanien pélkė (« boue »), le latin s-qualus."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "noun",
  "pos_title": "Nom commun",
  "senses": [
    {
      "glosses": [
        "Saleté, boue."
      ],
      "id": "fr-калъ-cu-noun-5ZVVIHPW"
    }
  ],
  "tags": [
    "masculine"
  ],
  "word": "калъ"
}

{
  "categories": [
    "Mots en vieux slave issus d’un mot en indo-européen commun",
    "Noms communs en vieux slave",
    "vieux slave",
    "Étymologies en vieux slave incluant une reconstruction"
  ],
  "derived": [
    {
      "lang": "Bulgare",
      "lang_code": "bg",
      "word": "кал"
    },
    {
      "lang": "Polonais",
      "lang_code": "pl",
      "word": "kał"
    },
    {
      "lang": "Tchèque",
      "lang_code": "cs",
      "word": "kal"
    }
  ],
  "etymology_texts": [
    "De l'indo-européen commun *kwal- qui donne le grec ancien πηλός, pêlós (« boue »), le lituanien pélkė (« boue »), le latin s-qualus."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "noun",
  "pos_title": "Nom commun",
  "senses": [
    {
      "glosses": [
        "Saleté, boue."
      ]
    }
  ],
  "tags": [
    "masculine"
  ],
  "word": "калъ"
}