The Spanish possessive adjective 'tu' meaning 'your' (singular, informal) comes directly from the Latin word 'tuus' with the same meaning. This word has remained remarkably stable in both form and meaning over the centuries, with just a slight simplification from 'tuus' to 'tu' as Latin evolved into Spanish.

This word is already one of the most basic and common words in Spanish, being one of the first possessive adjectives that students learn. It's related to the Spanish subject pronoun 'tú' (you, informal), though that word has a different Latin origin (from Latin 'tu').

While English 'your' is not directly related to Spanish 'tu', we can find a connection in the second person pronouns. English words like 'thou' (archaic for 'you') and 'thee' share an ancient Indo-European root with Spanish 'tu'. This shows how pronouns and possessives often have very ancient origins in language families.