The Spanish word 'murciélago' (meaning 'bat') has a fascinating etymology that comes from combining two Latin words: 'mus' meaning 'mouse' and 'caecus' meaning 'blind'. These words merged in Vulgar Latin to form 'murcaeculus', literally meaning 'little blind mouse' - a quite fitting description for how ancient Romans viewed bats!

The word evolved through Old Spanish 'murciégalo' before reaching its modern form 'murciélago'. This is a great example of how descriptive terms can evolve into standard animal names, as early observers likely noticed how bats seemed like blind mice flying through the dark.

While 'murciélago' itself is a common Spanish word, it's interesting to note that the original Latin 'mus' (mouse) developed differently in Spanish to become 'ratón' (mouse), taking a different etymological path. Therefore, despite the etymological connection to mice, modern Spanish doesn't preserve many obviously related simpler words.

English speakers might recognize a connection to the word 'mouse' since 'murciélago' partially comes from Latin 'mus'. This same Latin root gave us English words like 'mouse' and 'muscular' (originally referring to little mouse-like movements under the skin). The 'caec-' part of the etymology is related to English words like 'cecity' (blindness) and appears in scientific terms like 'caecilian' (a type of blind amphibian).