Early 16th century (in the sense 'indistinct, obscure'): from Latin ambiguus 'doubtful' (from ambigere 'waver, go around', from ambi- 'both ways' + agere 'to drive') + -ous.

• actor from Late Middle English:

  An actor was originally simply ‘a doer’, usually an agent or an administrator; the theatrical sense dates from the 16th century. Like act (Late Middle English) it comes from Latin actus ‘thing done’, which comes from agere ‘to do, drive’. This is the basis of other English words such as agenda (early 17th century) ‘things to be done’; agent (Late Middle English) ‘someone or thing who does things’; agile (Late Middle English) ‘able to do things’; agitate (Late Middle English) originally meaning ‘drive away’; ambiguous (early 16th century) ‘drive in both ways’, a word, which appears to have been coined by the English scholar and statesman Sir Thomas More (1478–1535), originally in the sense ‘indistinct, obscure’; transaction (Late Middle English) ‘something driven across or through’ and many more. Actuality (Late Middle English) originally had the sense ‘activity’; from Old French actualite from actualis ‘active, practical’. The modern French word actualité (usually meaning ‘news’) is sometimes used in English to mean ‘truth’, a sense not found in French as in: ‘When asked why the company had not been advised to include the potential military use, he [Alan Clark] said it was our old friend economical…with the actualité’ (Independent 10 November 1992).