The Spanish word 'abajo' meaning 'down' or 'below' comes from combining two elements: the prefix 'a-' meaning 'to/toward' and the word 'bajo' meaning 'low'. The word 'bajo' itself comes from Latin 'bassus' which meant 'fat' or 'short'. Over time, the meaning evolved from describing physical shortness to describing low position or height.

The simpler and very common Spanish word 'bajo' (meaning 'low' or 'under') is directly related to 'abajo', as 'abajo' is formed by adding the directional prefix 'a-' to 'bajo'. You'll also find this root in words like 'debajo' (underneath), 'bajada' (descent), and 'bajar' (to go down).

While English 'base' and 'bass' (as in bass note in music) come from the same Latin root 'bassus', they took slightly different semantic paths. 'Base' developed the meaning of 'lowest part' or 'foundation', while 'bass' specifically refers to low sounds or deep voices. The connection between Spanish 'abajo'/'bajo' and English 'base'/'bass' makes sense when you think about how they all relate to lowness or being at the bottom of something.