tranquilamente
/tɾanˌkilaˈmente/ · B2 · adv
calmly
🧘🌿 tranquil-a-mente = tranquil + mente (mind): with a still mind
Spanish adverbs add -mente to an adjective: tranquila + mente gives tranquilamente. Mente means mind, so the word reads as doing something in a mind-at-peace way. Same ending as English -ly.