abajo
/aˈbaxo/ · A1 · adv
down, downwards
⬇️ abajo = a (to) + bajo (low): to the low place, so down
Bajo means low or short, from Late Latin bassus, the same root as English base and bass. Add the preposition a (to) and you get to-low: down, below, downstairs. Its opposite arriba is built the same way: a + riba (bank, height).