The Spanish word 'baja' (meaning 'lowering' or 'decrease') comes from the Spanish verb 'bajar' meaning 'to lower.' This verb can be traced back to the Latin verb 'bassiare' meaning 'to lower,' which itself was derived from the Latin adjective 'bassus' meaning 'short and stout.' Over time, the Latin 'bassiare' evolved into Spanish 'bajar,' and 'baja' emerged as the feminine form and nominal form related to lowering or descent.

Some common related Spanish words include 'bajo' (low, or below), 'bajada' (descent or downhill), and 'bajito' (short or low). All these words share the same Latin root 'bassus' and maintain the core meaning related to lowness or descent.

While not immediately obvious, the English word 'base' is actually related to 'baja,' as it also comes from Latin 'bassus.' The meaning evolved differently in English, where 'base' came to refer to the bottom part or foundation of something, maintaining the connection to 'lowness' but in a more specific way. The musical term 'bass' (referring to low sounds) is another English relative, more directly reflecting the original Latin meaning of 'low.'