This article examines Russian dialect names for sour milk, ryazhenka (cooked sour milk), cooked fat-free milk and also colostrum (understood as a special condition of milk). The lexis of North Russian dialects (of the Arkhangelsk, Vologda and Kostroma regions) is represented the most fully. For each of the liquid dairy products the study identifies the motives of nomination, reveals non-trivial semantic transitions, and brings out individual and typical motivational models. It is established that the names of all liquid dairy products are linked on the denotative, motivational-semantic, and etymological levels. For example, the names for sour, fat-free and cooked milk share the same color motif of nomination; names for sour and fat-free milk are derived from stems with the meaning ‘cut, slash’ or from designations of poor quality food, etc. Words for sour milk and the process of acidification show the highest diversity of semantic motivation. They are derived from lexemes meaning ‘to push, to squeeze’, ‘to catch’, ‘to move, to start moving’, ‘to go down, to sit down’, ‘to roll upʼ, ʻto moisten, to get wet’, and so on. The article also addresses the interaction of the roots ser- and syr-, which figure in the designations of raw and sour milk, and in the northern territories — of colostrum.