adverbial (adj.)

"one of the indeclinable parts of speech, so called from being ordinarily joined to verbs for the purpose of limiting or extending their signification, but used also to qualify adjectives and other adverbs" [Century Dictionary], late 14c., from Late Latin adverbium "adverb," literally "that which is added to a verb" (to extend or limit its meaning), from ad "to" (see ad-) + verbum "verb, word" (from PIE root *were- (3) "to speak;" see verb). Coined by Flavius Sosipater Charisius as a translation of Greek epirrhema "adverb," from epi- "upon, on" + rhema "verb."