Dysphemism - -the substitution of an offensive or disparaging term for an inoffensive one.
Most deliberately abusive swearing involves the use of dysphemisms (for example, using "fucking nitwit" for "not so bright"; or, saying someone "fucking finally kicked the bucket" instead of the softer "he passed away.")
From *Expletive Deleted : A Good Look at Bad Language* by Ruth Wajnryb
"you mean like: 'that fucking scary ass shark just ate my best friend in one gulp!"
for, "that most charismatic of all fish, The Great Shark must have worked up quite an appetite swimming around, chomping on things: has anyone ever told him its condusive to eupepsia to chew your food thoroughly?"