WASP was originally spelled ‘waps’. 
BIRD was originally spelled ‘brid’. 
CURD was originally spelled ‘crud’. 
FRESH was originally spelled ‘fersc’. 
DIRT was originally spelled ‘drit’. 
THRILL was originally spelled ‘thirl’. 

The reordering of sounds like this is called METATHESIS.
(via @HaggardHawks)