The name 'Hoplr' (pronounce 'hopler') originates from the term 'city hopping'. Few people know this, but Hoplr started out as more of a neighbourhood and event calendar. Both inhabitants and non-inhabitants xere able to consult the activities of any city.
Hoplr can also refer to the English word 'hop': a link within a network. The neighbourhoods are the hops of the online neighbourhood network. This explanation obviously better suits Hoplr in its current form.
Other than that, it's just a fun name, so no acronym.