Generally, it seems that o as a suffix is masculine, with ai as feminine and e as gender neutral. Hence why oloth differs from olaith differs from oleth, but all are relatively interchangeable. Oloth means son. The added "til" is a number: one. You can see all the numbers by how they are listed for the rulers and in the rules of the realm document. Oloth-Til then means first-born son. Oloth-Vol would be second-born son.