perpendicular [LME] Those who remember school geometry lessons involving instructions to ‘drop a perpendicular’ may not be surprised to find that the source of this word is Latin perpendiculum ‘plumb line’, formed from per- ‘through’ and pendere ‘to hang’. The first recorded use of the loosened sense ‘very steep’ is found in Shakespeare’s ‘That sprightly Son of Scots, Douglas, that runs a-horseback up a hill perpendicular’ (Henry IV, Part I, Act 2 scene 5).