The term 'set off on a journey' can be summarized by two crossword solutions: 'EMBARK' (6 letters) and 'hit the road' (10 letters). EMBARK means to begin a journey, usually by boarding a ship or aircraft. It is derived from the Latin word 'embarcare', which means to board a ship. 'Hit the road' is an idiom that means to start a journey, usually by car. It is often used as a way of saying goodbye before a long journey.