Finnish kostaa

← German kehren (cognate)

← Proto-Finnic *kostadak (inherited)

← Proto-Indo-European *goys- (derived)

→ Finnish kostea (suffix)

→ Finnish kosto (suffix)

→ Finnish kostaja (suffix)

→ Finnish kostaminen (affix)

→ Finnish kostua (suffix)

→ Finnish koste (suffix)

→ Finnish kostautua (suffix)