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.
Breastfeeding protects babies from infections and illnesses that include diarrhea, ear infections and pneumonia. Breastfed babies are less likely to develop asthma. Children who are breastfed for six months are less likely to become obese. Breastfeeding also reduces the risk of sudden infant death syndrome (SIDS). Mothers who breastfeed have a decreased risk of breast and ovarian cancers.