Maybe this is my limitation, but it still looks like "love" means about the same at its core, thru the times - I don't see a "lost meaning" to it. But I do see "flavors" for love, if you will - motivations or contexts for the love. And I accept the point that "not every culture has written about love or valued it in the same way."

Yet the cited article does not indicate "love" as meaning "suffering for someone or something else" or anything like that. Instead, we get something about "tragic love" (an apparent "contradiction in terms"): "In the Middle Ages, the idea that suffering was in some way productive was very widespread."

Earlier in that article: "So what changed in the Middle Ages? 'There was a transformation in culture,’ said Professor Ashe. ‘A series of church reforms in the 12th century took Christianity from a rather austere view of God the Father to a new focus on Christ's humanity. 'The spiritual lives of ordinary people were recognised, and people were encouraged to have a more emotional and personal relationship with God as individuals. And romantic love - giving yourself to another person - provides a justification, in the medieval moral compass, for the pursuit of self-fulfilment as an individual."

And from there, I would argue, "passion" took on a definition of "love" (and not the other way round).