Also, in order to have a scientific definition of a second, the definition is as follows:
SI definition of second is “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom” Source
The Egyptians were the first to split the full cycle of day and night up into 24 hours, a system that was later improved upon by Greek astronomers Ptolemy and Hipparchus who further split it up in a sexagesimal (60 as a base) system, and that’s where the second comes into play. First you divide an hour into 60 parts, creating the minute, and then you divide that a second time, hence the name, creating 1/60th of a minute. Further splitting up a second in sixthieths is called a third, but that’s not really used nowadays.
At the time it wasn’t possible to keep time that accurate, but towards the end of the 16th century mechanical clocks were able to measure seconds accurately, which is also when the English word for them came into use.
Edit: Since so many people ask “Why use 60 as a base?”, the answer is because it’s easy to divide it by 2, 3, 4, 5, 6, 10, 12 15, 20 and 30, making it a solid base for counting.