Try used coffee grounds. Rub a handful onto the inside surface of the bowl and leave it for an hour or so before washing them off. If the bowl still smells rancid, coat it again with coffee grounds, but this time fill the bowl with luke-warm water and let it stand for a while, before rinsing it.
Be careful not to use water that is hot, as a wooden bowl, like anything else of unvarnished wood won't take kindly to really hot water.
You can scrub practically anything with used coffee grounds, including washing your hands with them if you have been chopping onions or doing some other "smelly" job. They don't dry your skin out either, which is an advantage too.