Glossary of Etymology Terms:
Acronym: creating a word from each letter of a phrase.
Backronym: creating a phrase from each letter of a word, many folk etymologies are backronyms.
Calque: an expression translated from another language, also, a new meaning for a word, taken from another language.
Eponym: a word or phrase coined after the name of a person.
Etymology: the branch of linguistics which deals with the evolution of words.
Folk etymology: a false etymology which is widely believed to be true. Also a change in the form of a word based on the assumption that the word is related to another word.
False friend: two words in different languages that are misleadingly similar in form, but have different meanings
Inflection: a suffix added to the end of a word to indicate certain grammatical aspects
Loanword: a word that is borrowed directly from another language without translation.
Prefix: a group of sounds added at the begginging of the stem of the word, such as -un in undecided.
Reconstruction: using comparative linguistics to reach hypothetical ancient forms for words in languages that were never written.
Substratum: a language which influences another one which eventually supplants it, such as Gaulish influencing the Latin spoken in France.
Suffix: a group of sounds added at the end of the stem of the word, such as -ness in happiness.
Toponym: the name of a geographical feature, a placename.