Popularized by Berkely Breathed's disturbing cartoon character "Bill the
Cat" of Bloom County fame (later became Outland). It is the product of the random misfirings of a braindead individual who wants to say something intelligent but seems completely devoid of any grey matter. It is frequently followed immediately by the word "thptptpt", which is produced by flatulations of either the lips or some other
sphincter.
You may also hear this exclamation muttered by hung-over frat-brothers when they first wake up.
You might also hear this word from
time to time in an overcrowded senior retirement center, with
nobody noticing it is even being said.