The Spanish word 'quilate' (meaning 'carat' or 'measure of purity') has an interesting journey through multiple languages. It originated from the Ancient Greek word 'kerátion', which meant 'little horn' or 'carob seed'. This connection to carob seeds isn't random - in ancient times, carob seeds were used as a standard unit of weight because they were believed to have very consistent mass.

The Greek term was borrowed into Arabic as 'qīrāṭ', maintaining both meanings of 'weight measure' and 'carob seed'. This then evolved into Andalusi Arabic 'qiráṭ', focusing on its meaning as a weight measure. Finally, it entered Spanish as 'quilate', where it came to specifically refer to the measurement of gold purity (as in 24-carat gold) or as a unit for weighing precious stones.

While 'quilate' is a relatively specific technical term in Spanish, it doesn't have many commonly used related words in modern Spanish. However, you might encounter it in jewelry-related contexts or when discussing precious metals and stones.

The English word 'carat' is a direct cognate of Spanish 'quilate', coming from the same Greek and Arabic origins. In English, like in Spanish, it has two main uses: measuring the purity of gold (as in 24-carat gold) and as a unit of mass for precious stones (where one carat equals 200 milligrams). The similar spelling and identical meaning make this an easy connection for English speakers to remember.