The Rice University Neologisms Database

One who participates in live action role playing games. (Those LARPers sure get into their games.) Possible reason used: 'Live action role playing' is a lengthy phrase, and those who wish to describe the activity might have grown tired of using it. Consequently, they began using the acronym 'LARP'. To describe one who participates in these games, they could use 'live action role player', but when used as an acronym, this must be distinguished from the primary use of 'LARP'. So to denote a live action role player, they added the '-er' suffix to the acronym 'LARP', treating 'LARP' like a morpheme rather than as an acronym. In the gaming community, it is common to use acronyms to shorten phrases. 'LARP' is a result of this tendency. This is most likely because it is easier to say an acronym like 'LARP' in casual conversation than to say an entire phrase. Additionally, the morpheme 'LARP' is not commonly heard outside of this gaming context, so even though it is an acronym, those who hear it in this context are likely to know its meaning.