It is just the usual way of introducing an unemphatic noun clause in the present or imperfect:
- Efallai bod nhw'n barod i fynd adref - Perhaps they were/are ready to go home
- Wrth gwrs bod nhw'n barod i ymddiheuro - Of course they are/were ready to apologise
- Ro'n i'n gwybod fod e'n barod i ymadael - I knew that he was prepared to leave
The construction is similar for noun clauses in other tenses:
- Ro'n i'n meddwl byddai fe wedi prynu car newydd erbyn diwedd y mis - I thought that he would have bought a new car by the end of the month
- Rydych chi'n gwybod bydd hi'n prynu cinio i ni i gyd ym Mhorthmadog - You know that she will buy lunch for us all in Porthmadog.