In Sanskrit sat means truth and the sangha is the group of lovers of Truth.
So satsang is literally a truth-gathering - an informal get-together of people to sit with the truth of their being, and occasionally, talk about it.
It's also like a sacrificial pit, or a recycling center. Things no longer required, if brought with sincerity - any suffering or confusion, identification or separation or old containers no longer needed - are left behind.
As Pamela has put it: Satsang is a gathering of mountains to discuss their mountain nature.