Dia daoibh,

I was wondering about the "darb" bit in sentences such as "an fear darb ainm Sean" where is the "d" coming from? Is it a combination of "do" and "arb"?

Also would it be correct to say "sin é an fear arbh fhuath leis a chat" ? As in, that's the man who hated his cat?

GRMA

Yes.
an fear darb ainm Seán
lit.: the man to-whom-is name Seán



Yes.

Examples from literature:
Lena chois sin ba shóisialaí dílis é Bing arbh fhuath leis an seicteachas. (Feasta)
... go dtí ceann de na cóisirí cocktail céanna arbh fhuath liom iad agus ar ghnách liom diúltú dóibh. (Róisín Ní Mheara-Vinard, Cé hí seo amugh?)
... a bhí fós ag déanamh géarleanúna ar Chríostaithe agus arbh fhuath leis ainm Íosa. (Donncha Ó Conchúir/Róisín Uí Chuill, Thar Táirseach an Dóchais Isteach)

Go raibh maith agat a Labhráis