"en" meaning in Proto-Celtic

{
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "cel-bry-pro",
            "2": "*ɨn"
          },
          "expansion": "Proto-Brythonic: *ɨn\nMiddle Breton: en\nBreton: e\nCornish: yn, en\nOld Welsh: in\nMiddle Welsh: yn\nWelsh: yn",
          "name": "desctree"
        }
      ],
      "text": "Proto-Brythonic: *ɨn\nMiddle Breton: en\nBreton: e\nCornish: yn, en\nOld Welsh: in\nMiddle Welsh: yn\nWelsh: yn"
    },
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "sga",
            "2": "i"
          },
          "expansion": "Old Irish: i, hí, hi\nIrish: i\nScottish Gaelic: an\nManx: ayns",
          "name": "desctree"
        }
      ],
      "text": "Old Irish: i, hí, hi\nIrish: i\nScottish Gaelic: an\nManx: ayns"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "cel-pro",
        "2": "ine-pro",
        "3": "*h₁én"
      },
      "expansion": "Proto-Indo-European *h₁én",
      "name": "inh"
    }
  ],
  "etymology_text": "From Proto-Indo-European *h₁én. Matasović reconstructs *eni for the whole preposition, but since the preposition triggers a nasal mutation/eclipsis instead of a lenition in its descendants, a closed syllable may be reconstructed instead. However, the attested closed syllable could be explained by the theory of the early apocope of final /i/ in unstressed words, usually used to explain the rise of the absolute and conjunct inflection in Old Irish (by treating conjunct forms in the unstressed category).",
  "head_templates": [
    {
      "args": {
        "1": "cel-pro",
        "2": "preposition"
      },
      "expansion": "*en",
      "name": "head"
    }
  ],
  "lang": "Proto-Celtic",
  "lang_code": "cel-pro",
  "original_title": "Reconstruction:Proto-Celtic/en",
  "pos": "prep",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Proto-Celtic entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Proto-Celtic prepositions",
          "parents": [],
          "source": "w"
        }
      ],
      "derived": [
        {
          "word": "eni-"
        }
      ],
      "glosses": [
        "in"
      ],
      "id": "en-en-cel-pro-prep-WClnU00P",
      "links": [
        [
          "in",
          "in"
        ]
      ],
      "tags": [
        "reconstruction"
      ],
      "wikipedia": [
        "Brill Publishers"
      ]
    }
  ],
  "word": "en"
}

{
  "derived": [
    {
      "word": "eni-"
    }
  ],
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "cel-bry-pro",
            "2": "*ɨn"
          },
          "expansion": "Proto-Brythonic: *ɨn\nMiddle Breton: en\nBreton: e\nCornish: yn, en\nOld Welsh: in\nMiddle Welsh: yn\nWelsh: yn",
          "name": "desctree"
        }
      ],
      "text": "Proto-Brythonic: *ɨn\nMiddle Breton: en\nBreton: e\nCornish: yn, en\nOld Welsh: in\nMiddle Welsh: yn\nWelsh: yn"
    },
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "sga",
            "2": "i"
          },
          "expansion": "Old Irish: i, hí, hi\nIrish: i\nScottish Gaelic: an\nManx: ayns",
          "name": "desctree"
        }
      ],
      "text": "Old Irish: i, hí, hi\nIrish: i\nScottish Gaelic: an\nManx: ayns"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "cel-pro",
        "2": "ine-pro",
        "3": "*h₁én"
      },
      "expansion": "Proto-Indo-European *h₁én",
      "name": "inh"
    }
  ],
  "etymology_text": "From Proto-Indo-European *h₁én. Matasović reconstructs *eni for the whole preposition, but since the preposition triggers a nasal mutation/eclipsis instead of a lenition in its descendants, a closed syllable may be reconstructed instead. However, the attested closed syllable could be explained by the theory of the early apocope of final /i/ in unstressed words, usually used to explain the rise of the absolute and conjunct inflection in Old Irish (by treating conjunct forms in the unstressed category).",
  "head_templates": [
    {
      "args": {
        "1": "cel-pro",
        "2": "preposition"
      },
      "expansion": "*en",
      "name": "head"
    }
  ],
  "lang": "Proto-Celtic",
  "lang_code": "cel-pro",
  "original_title": "Reconstruction:Proto-Celtic/en",
  "pos": "prep",
  "senses": [
    {
      "categories": [
        "Proto-Celtic entries with incorrect language header",
        "Proto-Celtic lemmas",
        "Proto-Celtic prepositions",
        "Proto-Celtic terms derived from Proto-Indo-European",
        "Proto-Celtic terms inherited from Proto-Indo-European"
      ],
      "glosses": [
        "in"
      ],
      "links": [
        [
          "in",
          "in"
        ]
      ],
      "tags": [
        "reconstruction"
      ],
      "wikipedia": [
        "Brill Publishers"
      ]
    }
  ],
  "word": "en"
}