The word has very positive associations in modern English, but these were sometimes lacking in the 16th century, where there was an additional sense of “over-confidence” or even “carelessness”. Without this negative resonance it is very difficult to make sense of Scroop’s caution to Henry V against forgiving the drunken man who had been abusive about the king:

“That’s mercy, but too much security” (Henry V, II.ii.44). The contrast with the modern meaning is strongest when the word is used along with another word that seems contradictory, as when Artemidorus warns Caesar that “security gives way to conspiracy” (Julius Caesar, II.iii.6) or Hecat advises her witches that “you all know securityIs mortals’ chiefest enemy” (Macbeth, III.v.32). The clash of senses is particularly striking when Aumerle says to Richard, “we are too remiss,Whilst Bolingbroke through our securityGrows strong” (Richard II, III.ii.34).

David Crystal is the author, with Ben Crystal, of Shakespeare’s Words, published by Penguin