Other forms: sharks
A shark is a big dangerous sea animal with many sharp teeth. A great white shark, shark attack, swim with sharks.
They have been around for over four hundred million years, predate trees, and replace their teeth continuously through life. Attacks on people are very rare and the reputation is out of all proportion. A loan shark lends at ruinous rates. Note that the origin of the word is genuinely unknown.
Too few real examples of this word to estimate which sense is commonest.
shark is a fish.
The word appears in English in the sixteenth century and its origin is unknown. A connection with a word meaning scoundrel has been suggested.
Middle English
shark
English, today
shark
From Middle English shark (used by Thomas Beckington in 1442 to refer to a kind of fish), of unknown origin. Most likely from a semantic extension of the German --derived shark (“scoundrel”), see below. The fish was originally called a dogfish or haye in English and Middle English. Its name in Old English is unknown, although some uses of the word hranfisċ that do not appear to carry the sense of "whale" may have been referencing it. 2 Some older dictionaries derived the word from Latin carcharias, carcharus (from Ancient Greek -), but admit that "the requisite [Old French] forms intermediate between E. shark and L. carcharus are not found, and it is not certain that the name [shark] was orig. applied to the fish; it may have been first used of a greedy man".
Etymology from Wiktionary, CC BY-SA