Origin of thalweg. German Talweg, Thalweg : Tal, Thal, valley (from Middle High German tal, from Old High German) + Weg, way (from Middle High German wec, weg, from Old High German weg; see wegh- in Indo-European roots).
Besides as Sandra said the natural age of weaning is older than 2 and the WHO advises breastfeeding for a minimum of 2 years. It is not ridiculous that your son wants milk at 22 months. I fed my oldest child until 2.5 and am still feeding my 18 month old and plan to keep going as long as I can.
Babies need whole milk until at least the age of 2, and breastmilk is whole milk, if you are still nursing then no other milk is needed. There are many benefits to nursing to 2 years and even longer!