The term 'Stiff UPPER Lip' is a phrase that has been used in English since the early 19th century. It is used to describe someone who is able to remain calm and composed in difficult situations, and is often associated with British stoicism. The phrase is derived from the Latin phrase 'strenuus summus labii', which translates to 'strong UPPER lip'. The crossword solutions for this phrase are UPPER, with five letters.