unweaned russian

• сосуно́к

  suckling, sucker (young animal), unweaned young

  greenhorn, novice, whippersnapper, kid

• сосу́н

  suckling, young (unweaned animal)

  greenhorn, whippersnapper, novice

• опо́ек

  calf leather, calfskin

  suckling calf, unweaned calf