Reconstruction:Proto-Slavic/loskъ

Resultant noun from Proto-Slavic *loskati (“to slap, to bash”), either of expressive origin related to Etymology 2 or possibly from *logъ +‎ *-skъ (as per Горох.ua). Compare Bulgarian разло́г (razlóg, “hollow”), Russian лог (log, “ravine”), ложби́на (ložbína, “depression”).

*loskъ m

1. dell, hollow

   Synonyms: *dolъ, *propastь

• *loščina (augmentative)

• *loskati (“to slap, to bash”)
• *loskunъ (“debris, remnant”)
• *loskutъ (“flap, clout”)

• East Slavic:
  • Old East Slavic: лоскъ (loskŭ)
    • Belarusian: лоск (losk), ло́скат (lóskat)
      • ⇒ Belarusian: лашчы́на (laščýna), лагчы́на (lahčýna)
    • Russian: лоск (losk) (dialectal лозг (lozg), instr. лозгом (lozgom))
      • ⇒ Russian: лощи́на (loščína)
    • Ukrainian: лоск (losk, “bump, unevenness, mess”) (probably)
      • ⇒ Ukrainian: лощи́на (loščýna)
• West Slavic:
  • Czech: Losky f (toponym)

• Trubachyov, Oleg, editor (1990), “*loskъ/*loska I”, in Этимологический словарь славянских языков [Etymological dictionary of Slavic languages] (in Russian), numbers 16 (*lokadlo – *lъživьcь), Moscow: Nauka, →ISBN, page 87
• лоск «безладдя» in Горох.ua (Етимологія)

Onomatopoeic.

*loskъ m

1. flap, bang, shriek

• *loska f

• *loskotъ (“chatter”)

• South Slavic:
  • Serbo-Croatian:

    Cyrillic script: лоска f

    Latin script: loska f

  • Slovene: lòsk (interjection)

• Trubachyov, Oleg, editor (1990), “*loskъ/*loska II”, in Этимологический словарь славянских языков [Etymological dictionary of Slavic languages] (in Russian), numbers 16 (*lokadlo – *lъživьcь), Moscow: Nauka, →ISBN, page 88