IIRC, Whatsapp is the first popular app of smartphone in Taiwan. In the beginning, A.P.P stand for Whatsapp in TV talk shows, just like F.B(Facebook) & I.G(Inst

IIRC, Whatsapp is the first popular app of smartphone in Taiwan. In the beginning, A.P.P stand for Whatsapp in TV talk shows, just like F.B(Facebook) & I.G(Instagram) nowadays. Hence people trend to spell the word app as A.P.P.. As more and more apps came out, the word app became more general, but the spelling didn't change at all.