In languages where the diminutive is productive (such as Slavic languages), many words derived as a diminutive have a meaning completely decoupled from their origin, and do not anymore "convey the smallness of the object or quality named, or a sense of intimacy or endearment" (diminutive). Even if the native speakers still might feel the relation, you cannot simply "de-diminutivate" them, you must use them in the exact diminutive form to get the new meaning.
Does this phenomenon have a name?
Examples in Czech:
- kohout (rooster) → kohoutek (tap)
- hlava (head) → hlávka (a piece of cabbage) → hlavička (head of nail, header in soccer)
- pomlka (pause) → pomlčka (dash)
- panna (virgin, also an obsolete term for a girl) → panenka (doll)
- slečna (miss) → slečinka (squeamish)
- hřeben (comb) → hřebínek (bird's crest)
- pár (couple) → párek (sausage)
- minuta (minute) → minutka (short order)
- kolo (wheel) → kolečko (wheelbarrow)
- zahrada (garden) → zahrádka (restaurant with outside seating)