I suppose it´s a drinking glass actually. The shape is very popular in middle continental
Europe. Likely made in one of the beer regions - Bohemia or Bavaria.
The trick is to empty it without wetting yourself. The critical point is, when you´ve emptied
it half-way and the air gets into the tip of the boot. This will - unless you know the knack -
produce a little wave, which will slop into the corners of your mouth and run down your
chin. Increasingly more difficult the later the evening and the amount you´ve drunk
already...

One of the smaller examples, they also come in large sizes. Try ´Trinkstiefel´ or ´Glasstiefel´
on ebay.de. I´m sure something similar will show up.