arriba
/aˈriba/ · A1 · adv
upstairs
⬆️ a + riba (riverbank): to the bank = up from the water
From Latin ad ripam, to the riverbank. Climbing out of a river means going up, so arriba came to mean up, above, upstairs. Same root as English arrive (reach the shore) and river. The cheer ¡arriba! is literally up with it!