Misnomer

A misnomer is a term that suggests an interpretation known to be untrue. Such incorrect terms sometimes derive their names because of the form, action, or origin of the subject becoming named popularly or widely referenced—long before their true natures were known.

Sources of misnomers
Some of the sources of misnomers are:
 * An older name being retained as the thing named evolved (e.g. pencil lead, tin can, fixed income market, mince meat pie, steamroller, tin foil, clothes iron, digital darkroom ). This is essentially a metaphorical extension with the older item standing for anything filling its role.
 * Transference of a well-known product brand name into a genericized trademark (e.g. Xerox for photocopy, Band-aid for adhesive bandage, Jell-o for gelatin dessert or Kleenex for facial tissue. In the UK, Hoover is often used for vacuum cleaner.).
 * An older name being retained even in the face of newer information (e.g. Chinese checkers, Arabic numerals).
 * Pars pro toto, or a name being applied to something which only covers part of a region. The name Holland is often used to refer to the Netherlands while it only designates a part of that country; sometimes people refer to the suburbs of a metropolis with the name of the biggest city in the metropolis.
 * A name being based on a similarity in a particular aspect (e.g. shooting stars (Meteors) look like stars from Earth, Greenland is icy and Iceland is greener).
 * A difference between popular and technical meanings of a term. For example, a koala "bear" (see below) looks and acts much like a bear, but from a zoologist's point of view it is quite distinct and unrelated. Similarly, fireflies fly like flies, ladybugs look and act like bugs. Botanically, peanuts look and taste like nuts. The technical sense is often cited as the "correct" sense, but this is a matter of context.
 * Ambiguity (e.g. a parkway is generally a road with park-like landscaping, not a place to park). Such a term may confuse those unfamiliar.
 * Association of a thing with a place other than one might assume.
 * Naming peculiar to the originator's world view.
 * An unfamiliar name (generally foreign) or technical term being re-analyzed as something more familiar.
 * Anachronisms, terms being applied to things that belong to another time, especially much later, such as the Dendera light interpretation of a mural from the Hathor Temple of Ancient Egypt.
 * Dispute of criteria on naming. For instance, freeways are generally divided highways with no at-grade intersections or private access, and expressways have no private access but select crossroads.  However, two-lane freeway often refers to 2-lane roads without private access that sometimes have at-grade intersections.

Older name retained

 * The "lead" in pencils is made of graphite and clay, not lead; graphite was originally believed to be lead ore but this is now known not to be the case. The graphite and clay mix is known as plumbago, meaning "lead ore" in Latin and is still known as "black lead" in Keswick, Cumbria and elsewhere.
 * Blackboards can be black, green, red or blue. The writing utensils typically used on them are no longer made of chalk, but of gypsum.
 * Tin foil is almost always aluminium, whereas "tin cans" made for the storage of food products are made from steel plated in a thin layer of tin. In both cases, tin was the original metal.
 * Telephone numbers are usually referred to as being dialed although rotary phones are now rare.
 * When a computer program is electronically transferred from disk to memory, this is referred to as loading the program. "Load" is a holdover term from the mid-20th century, when programs were created on punched cards and then loaded into a hopper for automated processing.
 * The electric generator does not actually generate electricity. It converts the one form of energy to other by electromagnetic induction.
 * In golf, the clubs commonly referred to as woods are usually made of metal. The club heads for "woods" were formerly made predominantly of wood.

Similarity

 * Guinea pigs are not pigs and do not come from Guinea. The "Guinea" may be a re-analysis of "Guyana", though they originate from the Andes and not Guyana.
 * Catgut is made from sheep intestines.
 * An egg cream is really chocolate flavored syrup with seltzer and milk. It typically contains neither eggs nor cream.
 * The English Horn is, in fact, neither English in origin nor a horn.
 * Head cheese is a meat product.
 * "Horny toads" or "horned frogs" are lizards.
 * A velvet ant is a type of wasp.

Difference between common and technical meanings

 * Koala "bears" are not bears. They are marsupials. The name "koala" is preferred in Australia, where koalas are native.
 * Jellyfish are not fish (but they do have a gelatinous structure similar to jelly).
 * Ringtail cats are not cats (Felidae), but rather are in the raccoon family (Procyonidae)
 * A peanut is not a true nut in the botanical sense, but a legume. Similarly, a coconut is not a true botanical nut.
 * Tear gas is not a gas, but a (solid) crystalline substance.

Association with place other than one might assume

 * Arabic numerals originated in India, though they came to be associated with the Arab world.
 * The Norway Rat (Rattus norvegicus) did not originate in Norway, but from North China.
 * French fries originated in Belgium, not in France.
 * French horns originated in Germany, not France.
 * Chinese checkers did not originate in China (nor in any part of Asia).
 * The Star of India, one of the largest star sapphires in the world was mined in Sri Lanka
 * Panama hats are made in Ecuador, but came to be associated with the building of the Panama Canal.

Reanalysis

 * In logic, begging the question is a type of fallacy occurring in deductive reasoning in which the proposition to be proved is assumed implicitly or explicitly in one of the premises. However, more recently, "begs the question" has been used as a synonym for "raises the question".
 * A quantum leap is properly an instantaneous change, which may be either large or small. In physics, it is the smallest possible changes that are of particular interest. In vernacular usage, however, the term is often taken to imply an abrupt large change.

Other

 * While dry cleaning does not involve water, the process does involve the use of liquid solvents.
 * A radiator usually transfers more energy by convection than by radiation.
 * The "funny bone" is not a bone—the phrase refers to the ulnar nerve.