"u-" meaning in Proto-Samoyedic

{
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "sel-pro",
            "2": "*ū-"
          },
          "expansion": "Proto-Selkup: *ū-",
          "name": "desc"
        }
      ],
      "text": "Proto-Selkup: *ū-"
    },
    {
      "depth": 2,
      "templates": [
        {
          "args": {
            "1": "sel-nor",
            "2": "ӯӄо"
          },
          "expansion": "Northern Selkup: ӯӄо",
          "name": "desc"
        }
      ],
      "text": "Northern Selkup: ӯӄо"
    },
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "mtm",
            "2": "у-",
            "tr": "u-"
          },
          "expansion": "Mator: у- (u-)",
          "name": "desc"
        }
      ],
      "text": "Mator: у- (u-)"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "syd-pro",
        "2": "urj-pro",
        "3": "*uje-"
      },
      "expansion": "Proto-Uralic *uje-",
      "name": "inh"
    }
  ],
  "etymology_text": "From Proto-Uralic *uje-.",
  "head_templates": [
    {
      "args": {
        "1": "syd-pro",
        "2": "verb"
      },
      "expansion": "*u-",
      "name": "head"
    }
  ],
  "lang": "Proto-Samoyedic",
  "lang_code": "syd-pro",
  "original_title": "Reconstruction:Proto-Samoyedic/u-",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Proto-Samoyedic entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "derived": [
        {
          "sense": "Selkup; Northern Selkup",
          "word": "ӯрӄо"
        },
        {
          "sense": "Selkup; Northern Selkup",
          "word": "ӯӄылтыӄо"
        },
        {
          "roman": "úrgu",
          "sense": "Southern Selkup",
          "word": "у́ргу"
        },
        {
          "roman": "uurgu",
          "sense": "Southern Selkup; Upper Ob",
          "word": "уургу"
        },
        {
          "alt": "ŋoxolăsʹ°",
          "sense": "Nenets",
          "word": "ӈохолӑсь"
        }
      ],
      "glosses": [
        "to swim"
      ],
      "id": "en-u--syd-pro-verb-cne7kYg8",
      "links": [
        [
          "swim",
          "swim"
        ]
      ],
      "tags": [
        "reconstruction"
      ]
    }
  ],
  "word": "u-"
}

{
  "derived": [
    {
      "sense": "Selkup; Northern Selkup",
      "word": "ӯрӄо"
    },
    {
      "roman": "úrgu",
      "sense": "Southern Selkup",
      "word": "у́ргу"
    },
    {
      "roman": "uurgu",
      "sense": "Southern Selkup; Upper Ob",
      "word": "уургу"
    },
    {
      "alt": "ŋoxolăsʹ°",
      "sense": "Nenets",
      "word": "ӈохолӑсь"
    },
    {
      "sense": "Selkup; Northern Selkup",
      "word": "ӯӄылтыӄо"
    }
  ],
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "sel-pro",
            "2": "*ū-"
          },
          "expansion": "Proto-Selkup: *ū-",
          "name": "desc"
        }
      ],
      "text": "Proto-Selkup: *ū-"
    },
    {
      "depth": 2,
      "templates": [
        {
          "args": {
            "1": "sel-nor",
            "2": "ӯӄо"
          },
          "expansion": "Northern Selkup: ӯӄо",
          "name": "desc"
        }
      ],
      "text": "Northern Selkup: ӯӄо"
    },
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "mtm",
            "2": "у-",
            "tr": "u-"
          },
          "expansion": "Mator: у- (u-)",
          "name": "desc"
        }
      ],
      "text": "Mator: у- (u-)"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "syd-pro",
        "2": "urj-pro",
        "3": "*uje-"
      },
      "expansion": "Proto-Uralic *uje-",
      "name": "inh"
    }
  ],
  "etymology_text": "From Proto-Uralic *uje-.",
  "head_templates": [
    {
      "args": {
        "1": "syd-pro",
        "2": "verb"
      },
      "expansion": "*u-",
      "name": "head"
    }
  ],
  "lang": "Proto-Samoyedic",
  "lang_code": "syd-pro",
  "original_title": "Reconstruction:Proto-Samoyedic/u-",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Proto-Samoyedic entries with incorrect language header",
        "Proto-Samoyedic lemmas",
        "Proto-Samoyedic terms derived from Proto-Uralic",
        "Proto-Samoyedic terms inherited from Proto-Uralic",
        "Proto-Samoyedic verbs"
      ],
      "glosses": [
        "to swim"
      ],
      "links": [
        [
          "swim",
          "swim"
        ]
      ],
      "tags": [
        "reconstruction"
      ]
    }
  ],
  "word": "u-"
}