The affix ūka comes in the sense of 'agent having such a habit etc.' after the verbs 1. yaj 2. jap 3. daś when they end in the affix y,
The intensives of these verbs take ऊक. As यायजूकः 'a performer of frequent sacrifices'; जञ्जपूकः 'a mutterer of prayers repeatedly'; दन्दशूकः 'a snake (what bites frequently)'.,