It's not idolatry, because 'idolatry' has a pretty strict definition. Worshipping anyone other than God is not Christian; worshipping a saint is not Christian;

It's not idolatry, because 'idolatry' has a pretty strict definition. Worshipping anyone other than God is not Christian; worshipping a saint is not Christian; worshipping a relic is not Christian. But venerating a saint or a relic of a saint has a long tradition, and can be understood not to be idolatry. If I keep a picture of my wife in my pocket, I'm not worshipping her. If I keep a lock of her hair in a locket around my neck, I'm not committing idolatry. If I worshipped the lock of her hair, that'd be idolatry.