'architrave' originates from Late Latin 'architrāvus', ultimately from Ancient Greek 'arkhitrabē' (ἀρχίτραβη), where 'arkhi-' meant 'chief' and 'trabē' meant 'beam'.

'architrabē' (Greek) changed into Latin 'architrāvus' in Late Latin, passed into Italian/French forms and then entered English as 'architrave' in the Early Modern period.

Initially it meant 'chief beam' or 'principal beam'; over time the term became specialized to mean the lowest part of an entablature in classical architecture and later was extended to refer to decorative door/window surrounds.