The Spanish word 'todo' meaning 'all' or 'entire' comes directly from the Latin word 'totus', which had the same meaning. This is a straightforward etymology where both the form and meaning have remained remarkably stable over time, with just a slight modification from 'totus' to 'todo' as Latin evolved into Spanish.

'Todo' is itself one of the most basic and common Spanish words, being used in many everyday phrases like 'todos los días' (every day) and 'del todo' (completely). It's also found in common compounds like 'todopoderoso' (almighty) and 'sobretodo' (overcoat, above all).

English speakers might recognize the Latin root 'totus' in words like 'total', 'totally', and 'totality'. While Spanish maintained the word as the everyday term for 'all', English borrowed these related words through French and Latin, primarily for more formal or technical contexts. The connection between Spanish 'todo' and English 'total' can help English speakers remember that 'todo' refers to something complete or entire.