Like we can save data on a SD card, people tried to save positivity in a object, so that it can be shared with everyone, ling/lingam is made from a particular material and have a particular shape, the shape its just an oval, like a planets orbit around its star, even if you observe Buddhist stupa is bigger version of the same..
There are elaborate processes of how to install positivity in that, prana pratista or mantra pratista
I have no scientific data on how to save positivity in an object , As a Vipassana meditator I feel my meditation session is very smooth when sitting around few Linga
Ling in Sanskrit refers to a thing, like female and male are referred to as Stri-Ling (woman kind, not women phallus) and Purusha-Ling(man kind)...
So Shiv-Ling mean It is representation of Shiva or what ever