Reconstruction:Proto-Slavic/čukъ

Possibly polygenetic. Proposed origins:

• For onomatopoiec meaning: From an expressive *čuti, *čьvati (“to bark, to wail”) +‎ *-kъ, parallel to Proto-Slavic *čuxъ (“growl, sniffle”). Per Snoj, probably ultimately from Proto-Indo-European *(s)kew- (“to wail, to shout”), akin to Lithuanian kaũkti (“to howl”), Latvian kàukt (“to yell, to howl”).
• For tool meaning: From Proto-Indo-European *kewh₂- (“to hew”), related to Proto-Slavic *kyjь (“hammer”).

*čȗkъ m^[1]

1. (onomatopoeic) knock, clatter, rumble

   → pigmy owl (in Western South Slavic)

2. hammer, mallet

   Synonyms: *kyjь, *moltъ

• *čukati (“to knock, to throb”)

• *kuka (“hook”)
• *čuka (“hilltop”)
• *čuxъ (“growl, sniffle”)
• *čupъ (“crack, crook”)
• *čubъ (“forelock”)

• East Slavic:
  • Russian: чук (čuk, “part of forelock”) (dialectal)
  • Ukrainian: чук (čuk, “rumble”)
• South Slavic:
  • Bulgarian: чу́к (čúk, “hammer; knock”)
  • Macedonian: чук (čuk, “knock”)
  • Serbo-Croatian:
    • Cyrillic script: чу̏к (dialectal), ћу̑к (“pigmy owl”)
    • Latin script: čȕk (dialectal), ćȗk (“pigmy owl”)
  • Slovene: čūk (“pigmy owl”)

• Trubachyov, Oleg, editor (1977), “*čukъ”, in Этимологический словарь славянских языков [Etymological dictionary of Slavic languages] (in Russian), numbers 4 (*čaběniti – *děľa), Moscow: Nauka, page 132