The Spanish word 'posdata' meaning 'postscript' comes from combining two Latin words: 'post' meaning 'after' and 'data' meaning 'given' (from the Latin verb 'dare' meaning 'to give'). When joined together, these elements literally mean 'given after' or 'that which is given afterwards', referring to text that is added after the main body of a letter or document.

A related and commonly used Spanish word is 'dato' (meaning 'data' or 'fact'), which comes from the same Latin root 'data'. You might also recognize this in words like 'datar' (to date) and 'fecha' (date).

English speakers will recognize both parts of this word in familiar terms. 'Post-' is a common prefix in English (as in 'postpone', 'posterior', 'postwar') coming from the same Latin 'post' meaning 'after'. The 'data' part is identical to the English word 'data', which also comes from Latin 'data' meaning 'things given'. The English abbreviation 'P.S.' (postscript) is actually a direct parallel to 'posdata', as both mean 'written after' and serve the same purpose.