The letter name is derived from proto-semitic ayn, "eye", and the phoenician letter had an eye-shape, ultimately derived from the IR hyerogliph.
To this day, ayn in hebrew, arabic, and amharic means "eye" and "spring" (ayno in neo-aramaic).
Because the sound is difficult for most non-arabs to pronounce, it is often used as a shibboleth by arabic speakers;
The word ayn, eye, ensures that this letter means perception and vision. Among all the organs, it is the eye that reveals most to men. And the wise say: "eino dome shmiya lereiya, the sense of hearing is not comparable to the sense of seeing. (source: Mechilta, Exodus 19:9)
The word ayn related to maayan, fountain, means also spring of water. (Genesis 16:7). Like a spring brings water from the depth of the earth to sunlight, so the eye brings perception of the world to the mind of men. (source: rav Hirsh, Genesis 3:5)
Ayn implores us to open our eyes, to see beyond the physical. The ayn is meant to take us from dark to light.
Below you can see the movie of the production process of a clay prototype of a hebrew letter. The prototype is then used to design the jewel.