Reconstruction:Proto-Slavic/-kati

• (after a consonant) *-ьkati / *-ьcati
• (assimilated form, with voiced */k/): *-gati

In Proto-Slavic, and probably Proto-Indo-European, many onomatopoeic sounds ended in */k/; for example:

• *bьlkъ! → *bьlkati, *bьlčǫ/bьlkajǫ (“to sound like a blazing fire or boiling water; to babble, chatter”)
• post-PIE *plāk- (“to beat, whip”) → *plakati, *plačǫ (sę) (“to beat, whip (oneself), cry, lament”)

This caused the suffix *-k- to be reinterpreted as having expressive/onomatopoeic meaning.

Cognate with Lithuanian -ke-, -kėti, Latin -ic- (as in e.g. fod-ic-ō) and Ancient Greek -κα- (-ka-). Similar to Proto-Germanic *-kōną (and from there with English -k, German -chen, etc) even though technically not cognates.

*-kati

1. Creates onomatopoeic verbs denoting an action of mimicking a sound in the root.

   *ble! → *blekati, *blečǫ/*blekajǫ (“to sound like a sheep”)

   *kra! → *krakati, *kračǫ (“to sound like a crow”)

   *kva! → *kvakati, *kvačǫ/*kvakajǫ (“to sound like a frog, crow or duck”)

2. Creates expressive and emotionally colored verbs.

   *bakati, *bakajǫ (“to shout, scold, chatter”) : *bajati (“to speak, order, bewitch”)

   *blǫkati, *blǫkajǫ (“to loiter, wander”) : *blǫditi (“id.”)

   *brukati, *brukajǫ (“to soil, pollute”) : *bruditi (“id.”)

   *čakati, *čakajǫ (“to wait”) : *čajati/*čati, *čajǫ (“id.”)

3. (by extension, from the previous meaning) Creates hypocoristic and and diminutive verbs.

   *běžati (“to run, quickly move”) → *běžьkati, *běžьkajǫ (“to walk, run”) (of children)

   *bosti, bodǫ (“prickle, prick”) → *bodьcati, *bodьcajǫ (“to often lightly poke”)

• *-čati (parallel formation with the same meaning)

• *-i-kati, -i-kajǫ (extended form)
• *-u-kati, -u-kajǫ (extended form)
• *-y-kati, -y-kajǫ (extended form)

• East Slavic:
  • Old East Slavic: -кати (-kati)
    • Belarusian: -каць (-kacʹ)
    • Russian: -кать (-katʹ)
    • Ukrainian: -кати (-katy)
• South Slavic:
  • Old Church Slavonic:

    Cyrillic: -кати (-kati)

    Glagolitic: -ⰽⰰⱅⰹ (-kati)

  • Bulgarian: -ка- (-ka-)
  • Macedonian: -ка- (-ka-)
  • Serbo-Croatian:

    Cyrillic: -кати

    Latin: -kati

  • Slovene: -kati
• West Slavic:
  • Czech: -kat
  • Polish: -kać
  • Slovak: -kať
  • Slovincian: *-kăc
  • Sorbian:
    • Lower Sorbian: -kać
    • Upper Sorbian: -kaś

• Sławski, Franciszek, editor (1974) Słownik prasłowiański (in Polish), volume I, Wrocław: Polska Akademia Nauk, page 49f