"-o-" meaning in Old Polish

{
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "pl",
            "2": "-o-"
          },
          "expansion": "Polish: -o-",
          "name": "desc"
        }
      ],
      "text": "Polish: -o-"
    },
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "szl",
            "2": "-o-"
          },
          "expansion": "Silesian: -o-",
          "name": "desc"
        }
      ],
      "text": "Silesian: -o-"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "zlw-opl",
        "2": "inh",
        "3": "sla-pro>*-o->interfix",
        "id": "interfix",
        "tree": "1"
      },
      "expansion": "Etymology tree\nProto-Slavic *-o-\nOld Polish -o-",
      "name": "etymon"
    },
    {
      "args": {
        "1": "Inherited"
      },
      "expansion": "Inherited",
      "name": "glossary"
    },
    {
      "args": {
        "1": "zlw-opl",
        "2": "sla-pro",
        "3": "*-o-",
        "4": "",
        "5": "",
        "g": "",
        "g2": "",
        "g3": "",
        "id": "",
        "lit": "",
        "nocat": "",
        "pos": "",
        "sc": "",
        "sort": "",
        "tr": "",
        "ts": ""
      },
      "expansion": "Proto-Slavic *-o-",
      "name": "inh"
    },
    {
      "args": {
        "1": "zlw-opl",
        "2": "sla-pro",
        "3": "*-o-"
      },
      "expansion": "Inherited from Proto-Slavic *-o-",
      "name": "inh+"
    }
  ],
  "etymology_text": "Etymology tree\nProto-Slavic *-o-\nOld Polish -o-\nInherited from Proto-Slavic *-o-",
  "head_templates": [
    {
      "args": {
        "1": "zlw-opl",
        "2": "interfix"
      },
      "expansion": "-o-",
      "name": "head"
    }
  ],
  "lang": "Old Polish",
  "lang_code": "zlw-opl",
  "pos": "interfix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Old Polish entries with etymology trees",
          "parents": [
            "Entries with etymology trees",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Old Polish entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Old Polish interfixes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 17 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "used in compound words"
      ],
      "id": "en--o--zlw-opl-interfix-yYkJPb0G",
      "tags": [
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɔ/",
      "note": "10ᵗʰ–15ᵗʰ CE"
    },
    {
      "ipa": "/ɔ/",
      "note": "15ᵗʰ CE"
    }
  ],
  "word": "-o-"
}

{
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "pl",
            "2": "-o-"
          },
          "expansion": "Polish: -o-",
          "name": "desc"
        }
      ],
      "text": "Polish: -o-"
    },
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "szl",
            "2": "-o-"
          },
          "expansion": "Silesian: -o-",
          "name": "desc"
        }
      ],
      "text": "Silesian: -o-"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "zlw-opl",
        "2": "inh",
        "3": "sla-pro>*-o->interfix",
        "id": "interfix",
        "tree": "1"
      },
      "expansion": "Etymology tree\nProto-Slavic *-o-\nOld Polish -o-",
      "name": "etymon"
    },
    {
      "args": {
        "1": "Inherited"
      },
      "expansion": "Inherited",
      "name": "glossary"
    },
    {
      "args": {
        "1": "zlw-opl",
        "2": "sla-pro",
        "3": "*-o-",
        "4": "",
        "5": "",
        "g": "",
        "g2": "",
        "g3": "",
        "id": "",
        "lit": "",
        "nocat": "",
        "pos": "",
        "sc": "",
        "sort": "",
        "tr": "",
        "ts": ""
      },
      "expansion": "Proto-Slavic *-o-",
      "name": "inh"
    },
    {
      "args": {
        "1": "zlw-opl",
        "2": "sla-pro",
        "3": "*-o-"
      },
      "expansion": "Inherited from Proto-Slavic *-o-",
      "name": "inh+"
    }
  ],
  "etymology_text": "Etymology tree\nProto-Slavic *-o-\nOld Polish -o-\nInherited from Proto-Slavic *-o-",
  "head_templates": [
    {
      "args": {
        "1": "zlw-opl",
        "2": "interfix"
      },
      "expansion": "-o-",
      "name": "head"
    }
  ],
  "lang": "Old Polish",
  "lang_code": "zlw-opl",
  "pos": "interfix",
  "senses": [
    {
      "categories": [
        "Old Polish entries with etymology trees",
        "Old Polish entries with incorrect language header",
        "Old Polish interfixes",
        "Old Polish lemmas",
        "Old Polish terms derived from Proto-Slavic",
        "Old Polish terms inherited from Proto-Slavic",
        "Old Polish terms with IPA pronunciation",
        "Pages with 17 entries",
        "Pages with entries"
      ],
      "glosses": [
        "used in compound words"
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɔ/",
      "note": "10ᵗʰ–15ᵗʰ CE"
    },
    {
      "ipa": "/ɔ/",
      "note": "15ᵗʰ CE"
    }
  ],
  "word": "-o-"
}