I said "chicken" instead of "hen." Is there a reason it must be "hen" to translate "iar"? It's not a word I use a lot in English.
'Chicken' is fine, too, for the adult bird wandering around the farm-yard. Cyw iâr is the usual term for chicken in a state to be eaten.
Iâr also pops up in terms like grugiar for 'grouse' (heather-hen).