The second is the base unit of time in the International System of Units. It is qualitatively defined as the second division of the hour by sixty. It is quantitatively defined as the time taken by 9,192,631,770 cycles of radiation that comes from electrons moving between two energy levels of the caesium-133 atom - the so-called atomic clock.
Until modern times scientists used the Latin terms "pars minuta prima" (first small part), "pars minuta secunda" (second small part), "pars minuta tertia" (third small part) and so on. This evolved to the modern "minute" and "second". The use of the word "second" in English began in the late 16th century.
Today, for smaller divisions we follow the decimal division, but in some languages, dictionaries still keep the word for third for 1/60 of a second.