Since the 1600s, the verb 'to wet' has meant to celebrate by drinking, though the earliest use of 'wet the baby's head' as such dates only to the 19th century.
When a baby is baptised, its head is literally 'wetted' by the priest, so the custom of fathers inviting friends to 'wet the baby's head' is just a sort of secular baptism, as it were.
Well, Dool, as the questioner himself says, to 'whet' means to sharpen as in 'whetstone' or in in 'whetting' someone's appetite. Sharpening a baby's head isn't altogether a good idea...at least not unless you plan to use it as a dart!
I have to say I loved your notion of 'wreckless' driving the other day! But believe me, I will draw attention to someone's spelling only when it seems to me to be amusing to do so. You haven't been around AB long enough to remember the bad old days!
The thing is I'm a secretary and I know I am a good spellerist (what you laughing at?!) so please stop picking on me because I HATE having my mistakes pointed out! I get it all day every day!
Quizmonster i like your answers. I also think that it does refer to Baptism as in the early 90s most people were Christian and celebrated babies and 'made them known to God' by baptism, so its now become a frequent phrase.
Hope this helped