OK / thank you / goodbye /
It is thought to be a made-up word combining iyi (good) and vallah (by God) and is very versatile. You can thank someone in a very heartfelt way by saying ‘eyvallah’ while touching your heart with your right hand or say ‘hadi bana eyvallah’ when you want to imply that you don’t want to be there anymore or to simply agree with what someone is saying. And not doing or having an ‘eyvallah’ (eyvallah etmemek/eyvallahı olmamak) is used to mean not owing any thanks/apologies and making your own decisions freely.