Alexei is a name of Slavic origin, specifically Russian and Ukrainian, derived from the Greek name Alexander. It means 'defender of mankind' or 'protector'. The name was popularized in Russia by Saint Alexius of Kiev, the first known Prince of Kiev who ruled around 860 AD. Throughout history, several prominent figures have borne this name, including Alexei I (1629-1676), the second Tsar of the Romanov dynasty.
"The name Alexei has seen a significant rise in popularity over the past five decades, with a notable spike occurring around the late 1990s to early 2000s. However, it experienced a slight decline after 2015."