every now and then
Synonym discussion
Sense: idiom/1
All four phrases describe actions that happen at irregular, widely-spaced moments. 'Occasionally' is the most neutral and can be used in formal writing or casual speech. 'From time to time' carries a slightly deliberate, reflective tone — suitable for describing habits one consciously maintains. 'Every so often' feels more conversational and often describes spontaneous or unplanned occurrences. 'Once in a while' emphasises the length of the gap between events ('once in a while I treat myself to a good steak'). 'Every now and then' is closest to 'every so often' in register but is slightly more common in spoken English and pairs naturally with words like 'still' or 'even now' to contrast a current behaviour with a past one.
Etymology
This phrase is built on the older adverb 'now and then' (recorded since the 1500s), where 'now' stands for 'at one time' and 'then' for 'at another time'. Adding 'every' before 'now and then' (first seen in the 1700s) strengthens the sense that each occurrence is a separate, isolated moment. The pattern 'every X and Y' for frequency is unique to English and gives the phrase its rhythmic, conversational feel.