Intentionally misspelled, this word is meant to sound like 'Caecum', a segment at the end of the mammalian digestive tract. When the snerd crowd got its hands on 'Caecum' after a chance mispronunciation in s/e bio class, they changed the spelling and used it as the brand name for a line of delicious munchkin-like snacks known as 'Cakeums' (see Epic Pwng). Among fellow snerds, Cakeum can refer to the body-part or the food.
"Looking at this diagram of the human digestive tract, you can see the Cakeum, located at the end the large intestine" (She obviously reffering to the body part)
"Yo, go in the cupboard and get me that half-full box of Cakeums" (He is obviously reffering to the delicious snack food)
"Oooohh...ooooh yeah, baby....yeah, oh baby, let me eat your cakeum!...let me eat it..." (Ummm...Its ambiguous)