PAO's are derived from a two-step process involving an ethylene gas, to a linear alpha-olefin, to olefin polymers.
It is one of the many Gas-to-Liquid processes for making lubricating fluids.
Ethylene is also known as ethene and olefiant gas.
BTW, Ray H had an excellent description in another thread:
quote: Folks, 1-decene homopolymer, hydrogenated IS the technical designation for PAO's. "1-decene" - the raw synthesized olefin building blocks; "homopolymer" - a chain of identical olefins built up to the desired molecular weight; hydrogenated -any "loose" (more correctly, "unbound") valence bonds in the chain have been saturated with hydrogen as protection against oxidation in use.