Mimicking of the Japanese pronunciation of the phrase "My Wife" ("Wife" is an English cognitive in Japanese, keeping it's pronunciation but adding a "u"). Originally uttered by Mr. Kimura in Azumanga Daioh. It is a common reply to a picture of any female character that the replier has feelings of attachment or endearment to. Now each anonymous has chosen their own waifu, usually the one that embodies the traits they desire most. Given the extreme ronery level of /a/, there are very few compromises regarding three-dimensional females. "Waifu Threads" are still common in boards such as /a/ and /c/.