The Spanish verb 'caer' (meaning 'to fall') comes directly from the Latin verb 'cadere', which also meant 'to fall'. Over time, as Latin evolved into Spanish, the medial '-d-' was lost and the ending simplified, resulting in the modern Spanish form 'caer'.

Several common Spanish words are related to 'caer', including: 'caída' (a fall), 'decaer' (to decline/decay), and 'recaer' (to relapse/fall again). These words all maintain the core meaning of falling or downward movement from the original Latin root.

English speakers might recognize the Latin root 'cadere' in words like 'cascade' (falling water), 'cadence' (the falling of rhythm or voice), 'decadent' (falling into decay), and 'accident' (literally something that 'falls' or happens by chance). The connection to falling or downward movement is preserved in these English derivatives, though sometimes in more metaphorical ways.