For some time now in the recent history of American English, people have been saying “based around” instead of the traditionally normative “based on.” This phrase can be heard almost daily on the media, uttered by speakers who seem to be in their twenties and thirties. Why this change in grammar?
Apparently, these speakers conceive of the passive mode of the verb base as denoting some sort of peripherality rather than the centrality/fundamentality commonly associated heretofore with this word. The latter, after all, means (according to the Merriam-Webster Dictionary Online) ‘the fundamental part of something; basic principle; essence, foundation, basis, groundwork’. The foundation of something is as central as one can get in the conceptual universe, is it not?
The shift in current speech must therefore be based on (take my grammar advisedly!) a reconceptualization of the verb. In the thinking of millennials et al., apparently resting on a foundation is conceived of as something tangential rather than central, i. e., covering the periphery of anything rested on (= its base), not on its core or center.