Short answers, pulled from the story.
The Latin word adverbium enters the English language through French to describe a specific grammatical function. This term combines the prefix ad- meaning 'to' with verbum meaning 'word' or 'verb'. The suffix -ium creates a nominal form that implies modification of verbs or verb phrases.
Thomas Edward Payne notes this etymology in his 1997 work Describing Morphosyntax: A Guide for Field Linguists published by Cambridge University Press. Rodney Huddleston and Geoffrey K. Pullum discuss these origins in their 2005 Student's Introduction to English Grammar from the same publisher.
An adverb generally modifies a verb, an adjective, another adverb, a determiner, a clause, a preposition, or a sentence. These words express manner, place, time, frequency, degree, or level of certainty. They answer questions such as how, when, where, or to what extent.
The major exception remains the function of modifying nouns which belongs to adjectives instead. Compare she sang loudly with her loud singing disturbed me. In the first instance the verb sang receives modification from the adverb loudly while the second sentence uses the adjective loud to modify the noun singing.
Dutch adverbs maintain the basic form of their corresponding adjectives without inflection though comparison sometimes occurs. German defines adverbs differently than English usage allows. Scandinavian languages typically derive adverbs by adding -t to make them identical to neuter adjective forms.