The people who lived in the ancient Babylon and Egypt, they used their body parts and natural surroundings for measurement of everything as they did not had the tools like measuring tape, ruler, etc. used in the modern world. Body parts like the cubit, the handspan, the palm and the fingers were used for the measurement of things.
Cubit – The part between the elbow and the tip of the middle finger of an adult person’s forearm.
Handspan – The length between the tip of the thumb and the tip of the little finger of an outstretched hand.
Palm – The width of the hand.
Fingers or digits – The width of the middle finger.
The Greeks developed a foot as their fundamental unit of length. The foot was the length of an adult person’s bare foot. To measure time, they observed the movements of the sun, the moon, the stars and other heavenly bodies.
But later on, in the medieval period, one of the most popular systems were built for measurement, named the British traditional system known as the foot-pound-second (FPS) system. It was named after three fundamental physical quantities – foot as length, pound as mass, second as time. Each foot was made of 12 inches, each inch like the length of three barleycorns placed back to back.

Need to standardize units

As time passed, the scientific measurements started to occur, but a problem arised when the traditional units like foot, handspan, cubit, etc. were not appropriate for deep measurements as the size of everybody’s body is different and can create a great confusion. Then, slowly-slowly, people felt to have fixed measurements throughout the world to avoid confusion.

The Metric System (Physical Quantities & Measurement | Physics | KnockLedge)

In the year 1791, the French Academy of Sciences developed a system known as the metric system. This was designed to fulfil the daily usual measurement as well as for the measurements used in scientific experiments. The unit of length was named as metre, and that is why this system is named as the metric system. The unit of mass was introduced as gram and the unit of volume/capacity was named as litre.

The MKS and CGS systems

As time passed, the metric system was divided into the MKS and the CGS systems. The system of measurement based on the metre-kilogram-second (MKS) units was the MKS system, whereas, the system of measurement based on the centimetre-gram-second (CGS) units was the CGS system.

The International System

During the twentieth century, the MKS system became more popular than the CGS system, but again there was a need to have just one universally accepted system for non-confusing measurements. So later on, in 1960, the General Conference of Weights and Measures met at Paris, in France and developed the International System of Units, also known as the SI System. All the seven fundamental physical quantities lie in the SI System.

Multiples and Submultiples of Units

Sometimes, we need to choose a unit which is smaller or maybe bigger than a fundamental physical quantity of the SI System for measurement of an unknown value. Like, if we want to measure the distance between two cities then metre will fall short. Same way, if we want to find out the thickness of a wire then metre will be too much. So for that reason, the multiples and submultiples of the SI unit have been made. Multiples are used for bigger measurements by creating bigger forms of the SI unit and submultiples (factors) are made into smaller forms of the SI unit for measurements accordingly.

E.g. – Centimetre is a submultiple of a metre and a kilometre is a multiple of the same. Therefore, centi means a hundredth part (1/100) and kilo means a thousand times (1000) of a metre.