Etymological processes

Word creation
Many strategies exist by which new words can be created.
 * Eponyms: Words named after people. For example, diesel fuel is named after Rudolf Diesel, who invented the first diesel engine.
 * Toponyms: Words named after places. For example, a donnybrook (a rowdy fight) is named after a location in Ireland.
 * Onomatopoeia: A word which mimics a sound (e.g., English bang)
 * Reduplication: This process yields words which have two almost-identical halves, like super-duper, hocus-pocus, or helter-skelter.
 * Blend: A word formed by combining portions of other words (e.g., English cyborg from cybernetic organism)
 * Portmanteau: A special kind of blend in which the beginning of one word is combined with the ending of another (e.g., English staycation from stay + vacation)
 * Back-formation: When a "simpler" word is created from a more "complex" word, such as the verb edit being created from editor, or the verb enthuse being created from enthusiastic.

Word evolution
Over long spans of time, words always change and evolve&mdash;sometimes in strange or confusing ways! Below are some of the etymological processes which commonly act upon words after they have been created.

Phonological
Some etymological processes change the way a word sounds.
 * Assimilation: Two sounds within a word becoming more similar (e.g., Latin octo 'eight' &rarr; Italian otto 'eight')
 * Dissimilation: Two sounds within a word becoming less similar (e.g., English chimney &rarr; English chimley (in some dialects))
 * Metathesis: Two sounds within a word switching place (e.g., Old English bridd&rarr; Modern English bird)

Morphological
Some etymological processes change the morphemes- the "parts"- inside of a word.
 * Folk etymology: This often occurs when one morpheme in a given word is unfamiliar and gets replaced by a more familiar morpheme, e.g. chaise lounge was originally Fr. chaise longue, meaning "long chair"

Semantic
Some etymological processes change the meaning of a word.
 * Semantic widening: When a specific word loses its specific meaning and instead gets applied in a general sense. This often occurs with brand names which become generic, like xerox or kleenex.
 * Semantic narrowing: When a general word takes a very specific meaning. e.g. deer comes from P.Gmc. *deuzam, which was the generic word for "animal".
 * Elevation (a.k.a. amelioration): When a word's connotation becomes more positive over time. The word democrat was viewed as negatively as the word demagogue in the 18th century, but by the 19th century, it was "rehabilitated" enough to be incorporated into the names of political parties.
 * Degeneration (a.k.a. pejoration): When a word's connotation becomes more negative over time. The word knave used to simply mean "boy," but now has connotations of someone dishonest or untrustworthy.
 * Metaphorical extension: When an old word is applied in a brand new context. An example would be a space ship, which may have a captain, a bridge, a hull, etc. These words are borrowed from the realm of sailing.