Although the word ‘critical’ had already been used in medicine to denote a very serious or acute state of a patient’s health, many scholars believe it first shows up in print as a term expressing disapproval or adverse judgments, in Act 2, Scene 1 of Othello, the Moor of Venice, a tragedy in five acts written by William Shakespeare. In that scene, Iago says to Desdemona: “O gentle lady, do not put me to’t; For I am nothing, if not critical.” Although Othello is believed to have been written by Shakespeare sometime in 1603–1604, it was first published in 1622.
Some scholars attribute the invention of many words to Shakespeare (see, for example, The LitCharts Blog) and it was not uncommon for authors to invent words. However, it was also not unusual to find that words used in everyday language at the time, might first find there way into recorded literature through some famous author and sometimes in imaginative ways – poetic license, perhaps!