Learn English – What does the slang term “Joe Gland” mean

Theory 1: It's a contraction of "what are you up to" or "what are you doing". Basically, the last part (up to/doing) is completely dropped, and the rest is smushed together.

Theory 2: it's short for "what cheer", purportedly 17th century slang for "what's up".

http://www.urbandictionary.com/define.php?defid=1058973&term=wotcher

EDIT:

The MSN Encarta dictionary and freedictionary.com support Martha's second theory that wotcher is contraction of "what cheer". It is a slang (U.K.) that means the same as hello. It should be noted that it is not clear whether the slang is still in use anywhere in the U.K.

I was in the military, but not Viet-Nam era. From my own judgment, I don't think it has anything to do with odometers. I think it's a dark humor reference.

When sighting in an M-16, the sights are adjusted in clicks. Looking downrange at a calibrated 100 yard target, one click moves the projectile/impact one inch across the face of the target. (left/right/up/down)

In the same way, when looking at a topo map, one "klick" is one full increment line on the map.

So viewed from the sky, (the point of view of either God or an enemy bomber, however you wish to imagine it) when we go one kilometer, we've traveled one click across the face of the map. The unspoken implication is that in the end we all might just be points on someone else's target...

Simply my opinion, but that's how it struck me the first time I heard it.