The Spanish word 'vaga' meaning 'wave' traces its origins through French 'vague' (meaning 'wave'), which ultimately comes from Old Norse 'vaag', also meaning 'wave'. This maritime term has maintained its basic meaning of a moving body of water across these different languages and time periods.

In Spanish, 'vaga' is relatively straightforward and doesn't have many simpler related words. However, it's worth noting that while 'vaga' refers to a wave, it's less commonly used than the more frequent Spanish word 'ola' for wave.

English speakers might recognize the connection to the word 'vague', which comes from the same French word 'vague'. While the English word evolved to mean 'unclear' or 'indefinite', this semantic shift makes sense when you think about how waves can blur and obscure what's beneath them. The wavy, unclear motion of water likely influenced the development of the English meaning.