"síi" meaning in Old Irish

{
  "etymology_templates": [
    {
      "args": {
        "1": "sga",
        "2": "cel-pro",
        "3": "*swīs"
      },
      "expansion": "Proto-Celtic *swīs",
      "name": "inh"
    },
    {
      "args": {
        "1": "cy",
        "2": "chwi"
      },
      "expansion": "Welsh chwi",
      "name": "cog"
    },
    {
      "args": {
        "1": "sga",
        "2": "ine-pro",
        "3": "*wos"
      },
      "expansion": "Proto-Indo-European *wos",
      "name": "inh"
    },
    {
      "args": {
        "1": "la",
        "2": "vōs"
      },
      "expansion": "Latin vōs",
      "name": "cog"
    },
    {
      "args": {
        "1": "cu",
        "2": "вꙑ"
      },
      "expansion": "Old Church Slavonic вꙑ (vy)",
      "name": "cog"
    }
  ],
  "etymology_text": "From Proto-Celtic *swīs (compare Welsh chwi), from Proto-Indo-European *wos (compare Latin vōs, Old Church Slavonic вꙑ (vy)).",
  "forms": [
    {
      "form": "sethar",
      "tags": [
        "genitive"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "sga",
        "2": "pronoun",
        "3": "genitive",
        "4": "sethar",
        "cat2": "personal pronouns"
      },
      "expansion": "síi (genitive sethar)",
      "name": "head"
    }
  ],
  "lang": "Old Irish",
  "lang_code": "sga",
  "pos": "pron",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Old Irish entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Old Irish personal pronouns",
          "parents": [
            "Personal pronouns",
            "Pronouns",
            "Lemmas"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Old Irish pronouns",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "you (nominative plural), ye"
      ],
      "id": "en-síi-sga-pron-fRsHa0n9",
      "links": [
        [
          "you",
          "you"
        ],
        [
          "ye",
          "ye"
        ]
      ],
      "related": [
        {
          "tags": [
            "emphatic"
          ],
          "word": "sibsi"
        },
        {
          "tags": [
            "emphatic"
          ],
          "word": "sissi"
        }
      ],
      "synonyms": [
        {
          "word": "sib"
        },
        {
          "word": "sí"
        }
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/sʲiː/"
    }
  ],
  "word": "síi"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "sga",
        "2": "cel-pro",
        "3": "*swīs"
      },
      "expansion": "Proto-Celtic *swīs",
      "name": "inh"
    },
    {
      "args": {
        "1": "cy",
        "2": "chwi"
      },
      "expansion": "Welsh chwi",
      "name": "cog"
    },
    {
      "args": {
        "1": "sga",
        "2": "ine-pro",
        "3": "*wos"
      },
      "expansion": "Proto-Indo-European *wos",
      "name": "inh"
    },
    {
      "args": {
        "1": "la",
        "2": "vōs"
      },
      "expansion": "Latin vōs",
      "name": "cog"
    },
    {
      "args": {
        "1": "cu",
        "2": "вꙑ"
      },
      "expansion": "Old Church Slavonic вꙑ (vy)",
      "name": "cog"
    }
  ],
  "etymology_text": "From Proto-Celtic *swīs (compare Welsh chwi), from Proto-Indo-European *wos (compare Latin vōs, Old Church Slavonic вꙑ (vy)).",
  "forms": [
    {
      "form": "sethar",
      "tags": [
        "genitive"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "sga",
        "2": "pronoun",
        "3": "genitive",
        "4": "sethar",
        "cat2": "personal pronouns"
      },
      "expansion": "síi (genitive sethar)",
      "name": "head"
    }
  ],
  "lang": "Old Irish",
  "lang_code": "sga",
  "pos": "pron",
  "related": [
    {
      "tags": [
        "emphatic"
      ],
      "word": "sibsi"
    },
    {
      "tags": [
        "emphatic"
      ],
      "word": "sissi"
    }
  ],
  "senses": [
    {
      "categories": [
        "Old Irish entries with incorrect language header",
        "Old Irish lemmas",
        "Old Irish personal pronouns",
        "Old Irish pronouns",
        "Old Irish terms derived from Proto-Celtic",
        "Old Irish terms derived from Proto-Indo-European",
        "Old Irish terms inherited from Proto-Celtic",
        "Old Irish terms inherited from Proto-Indo-European",
        "Old Irish terms with IPA pronunciation",
        "Old Irish terms with usage examples"
      ],
      "glosses": [
        "you (nominative plural), ye"
      ],
      "links": [
        [
          "you",
          "you"
        ],
        [
          "ye",
          "ye"
        ]
      ],
      "synonyms": [
        {
          "word": "sib"
        }
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/sʲiː/"
    }
  ],
  "synonyms": [
    {
      "word": "sí"
    }
  ],
  "word": "síi"
}