The Blue Large-Amplitude Pulsators ( BLAPs ) constitute a new class of pulsating stars .
They are hot stars with effective temperatures of \sim 30 000 K and surface gravities of \log g \sim 4.9 , that pulsate with periods in the range 20 - 40 min .
Until now , their origin and evolutionary state , as well as the nature of their pulsations , were not been unveiled .
In this paper , we propose that the BLAPs are the hot counterpart of the already known pulsating pre-Extremely Low Mass ( pre-ELM ) white dwarf ( WD ) stars , that are He-core low-mass stars resulting from interacting binary evolution .
Using fully evolutionary sequences , we show that the BLAPs are well represented by pre-ELM WD models with high effective temperature and stellar masses \sim 0.34 M _ { \sun } .
From the analysis of their pulsational properties , we find that the observed variabilities can be explained by high–order nonradial g - mode pulsations or , in the case of the shortest periods , also by low–order radial modes , including the fundamental radial mode .
The theoretical modes with periods in the observed range are unstable due to the \kappa mechanism associated to the Z -bump in the opacity at \log T \sim 5.25 .