An Oxymoron is a combination of contradictory or incongruous words, such as Cruel Kindness or Jumbo Shrimp. It is a literary figure of speech in which opposite or contradictory words, terms, phrases or ideas are combined to create a rhetorical effect by paradoxical means.
The word Oxymoron is originally derived from the Greek elements: oxy = sharp and moros (moron) = dull (foolish). Oxymoron is the singular form and Oxymora (or Oxymorons) is the plural form. So the word Oxymoron itself is an Oxymoron.
Some Oxymorons are not obvious, some may require an understanding of verbal or regional interpretations, and some may even indicate certain prejudices. Oxymorons are not necessarily mistakes or errors. They make effective titles and appealing phrases, and some are meant to be humorous.
In Jumbo Shrimp, Jumbo means large while Shrimp means small. But these two contradictory terms are combined to form a rhetorical phrase.
In this same way, Cruel Kindness has been formed with two contradictory terms Cruel & Kindness.