What Does it Mean to "Wet Your Whistle?" : Archae-Facts 

Sorry that I'm 10 years late. I think it might be because in order to whistle, one must first wet their lips. Otherwise whistling may be challenging. Therefore, a wet whistle, is better than a dry whistle. And your lips tend to become moist after drinking liquid. It's a long shot, and it's probably just the throat thing that you mentioned. But 10 years ago, I only watched the first 1 minute and 30 seconds of this video, before diving into my deep and meticulous research into the matter. Only to come back 10 years later, having finally discovered this possibility, thinking I'd finally cracked the code. But upon watching the last minute and 14 seconds, it's clear to me that the throat thing, something I hadn't yet considered, is indeed, a rather likely explanation, much more likely than mine perhaps. I fear we may never find out. Good luck. My quest continues.