Strange Occupation?

[Pennant]

Thank you very much. It looks like the right one (given that William Piers son of William is the one underneath in the transcription). But my Latin is very sparse. "decimo" in Spanish means tenth, so I'm guessing it might have come from the same word. Is the next word "octavo" - eighth? But basically I've no idea.

Added: what does bestiarii mean?

[Gillg]

 Bestiarii was the name given by the ancient Romans to those fighting wild beasts.   They were usually criminals, who were to be executed in this way.  But it was also a term used to describe the people who looked after the animals or the gladiators who specialised in fighting wild animals, so maybe he was an animal trainer!   
http://www.tribunesandtriumphs.org/gladiators/bestiarii.htm

[Watson]

I think in this context it would be someone who kept a herd of animals.

[JenB]

Looking again at the writing on the original, I don't think its 'bestiarii' I think it might be 'vestiarii' which would probably translate loosely as someone who made or dealt in clothes.

[Watson]

Yes, I agree vestiarii   It can mean a keeper of a vestry in an ecclesiastical sense.

[arthurk]

Another vote for vestiarii. I suspect he was just a run of the mill tailor - a keeper of ecclesiastical vestments seems more appropriate to a large cathedral than a small place like Llandyrnog.

[Watson]

Yes, I agree vestiarii in this context is not likely to have its ecclesiastical meaning.

[Pennant]

Thank you all very much for your helpful comments. It didn’t occur to me that they would have “transcribed” a translation (or mistranslation).