Reconstruction:Proto-Slavic/polъ

Probably from Proto-Balto-Slavic, possibly from Proto-Indo-European *(s)pelH- (“to chop, to separate”). Compare Proto-Slavic *polъka, *polica (“shelf, file”); see Lithuanian spãlis (“flax boon; October”) for more potential cognates.

*pólъ m^[1][2][3]

1. side, flank

   *na onomь polu ― on [the] yonder side

2. half

   *orzděľati polъma ― to divide in two

3. member of a pair of options → gender, sex

Secondarily:

• *pola (“moiety”)
• *polovъ (“halved”)
  • *poloviti (“to behalf”)
  • *polova, *polovina (“half”) (quantity)
• *polъ-, *polu- (“half-, semi-, mid-”)
  • *polъtora (“one and a half”)
  • *poludьnь, *polъdьne, *poldьnь (“midday”)
  • *polъnoťь, *polunoťь (“midnight”)
  • *polugodьje, *polъročьje (“half-year”)
• *polěno

• Vasmer, Max (1964–1973) “пол”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress
• Duridanov, I. V., Racheva, M., Todorov, T. A., editors (1996), “пол¹ (gender), пол² (half)”, in Български етимологичен речник [Bulgarian Etymological Dictionary] (in Bulgarian), volume 5 (падѐж – пỳска), Sofia: Prof. Marin Drinov Pubg. House, →ISBN, page 489

Either identical with Etymology 1 or from Proto-Indo-European *pel- (“to cover, to span, to fold”), *pleh₂- (“to flatten”).

*pólъ m^[1][2]

1. expanse, extent, plane
2. (by specialization) floor

   Synonym: *podъ

• *polovica (“stretch, strip”)

• *polti (“to fold, to twine”)
• *pelena (“nappy”)
• *plěna (“membrane”)
• *polsa (“strip”)
• *poľe (“field”)
• *polnina (“mountain”)

• East Slavic:
  • Belarusian: пол (pol)
  • Russian: пол (pol)
  • Ukrainian: пол (pol)
• South Slavic:
  • Bulgarian: поли́ pl (polí, “fells, slopes (of mountain)”)

• Vasmer, Max (1964–1973) “пол”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress
• Duridanov, I. V., Racheva, M., Todorov, T. A., editors (1996), “пола”, in Български етимологичен речник [Bulgarian Etymological Dictionary] (in Bulgarian), volume 5 (падѐж – пỳска), Sofia: Prof. Marin Drinov Pubg. House, →ISBN, page 491