Irish cream liqueur contains whiskey (typically Irish, such as Jameson brand), sugar and cream, or some sort of dairy. Then there is typically cocoa, vanilla and “other flavorings”.   When you look up copycat recipes for the original Bailey’s Irish Cream you will find sweetened condensed milk used quite a bit (but that isn’t low FODMAP), chocolate syrup (usually not a very high-quality product) and very often instant coffee as well.