"cork hat" means: A hat with bottle corks dangling from strings attached to the brim, traditionally worn in the bush to keep flies away from one's face.. This is a fairly neutral word with no inherent risk attached. There is no real cause for parental concern; it is descriptive vocabulary rather than something dangerous. If your child uses it, context will usually make the meaning clear. A brief, curious question about where they heard it is generally enough to know whether to follow up.