Sainfoin is an interesting name in itself, and comes from the French words meaning "Holy Hay" (Saint Foin)
Well, not quite. Sainfoin is French comes from the adjective "sain" meaning sane, healthy and yes "foin", hay. So, yes "healthy hay", but not "holy hay".
In French, Onobrychis viciifolia is usually called "sainfoin cultivé" (cultivated sainfoin). It is also called "esparcette à feuilles de vesce", which I found a beautiful name.
Nice to have someone who speaks French, you know how the internet is! Healthy Hay it is!