Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
shark (n.)
The fish’s name dates from the sixteenth century, but its ferocity, appetite, and reputation led subsequently to several pejorative transferred senses, particularly involving those who prey on others, as do loan sharks, pool sharks, and the like. But early in this century, U.S. college students began to use the noun to refer to classmates who excelled in a particular subject: Only a math shark could ace that exam. He’s a shark at history. When you use shark, be sure that context makes clear whether you intend it as a compliment or an insult.
