They each have one or two dozen topics. Assuming we don't want to merge them (because it is a type of meditation and a word which people will search for), should they at least be defined as synonyms?
What about jhana (three dozen topics) which is described as a type of samatha meditation: should that be a synonym too?
What about samadhi too (see also What is the difference between samadhi and samatha?), should that be a synonym of samatha?
And there's also mindfulness (seven dozen questions)?