loud (adj.) Look up loud at Dictionary.com
Middle English, from Old English hlud "noisy; making or emitting noise" (of voices, musical instruments, etc.), from West Germanic *khluthaz "heard" (source also of Old Frisian and Old Saxon hlud, Middle Dutch luut, Dutch luid, Old High German hlut, German laut "loud"), from PIE past participle *klutos- (source also of Sanskrit srutah, Greek klytos "heard of, celebrated," Latin inclutus "renowned, famous," Armenian lu "known," Irish cloth "noble, brave," Welsh clod "praise, fame"), from root *kleu- "to hear" (see listen (v.)).

Of places, "noisy," from 1590s. Application to colors, garments, etc. ("flashy, showy") is by 1849. Also used colloquially of notably strong or bad smells. Paired with clear (adj.) since at least c. 1650.
loud (adv.) Look up loud at Dictionary.com
Old English hlude "loudly, noisily," from Proto-Germanic *khludai (source also of Dutch luid, German laut), from the source of loud (adj.).