It is not that people were not expressing desire before christianity. Not that people did not have stronger desire for some than for others, wanted to be together with that person..etc..but that the use of the word is from the churches translations of the ancient greek philosophers.
Their so called "kinds of love"; "agape" and the like. (pisses in the direction of it)
The word "love" then became something of a double entendre. The church did this for several reasons, one of which was to control peoples desire, by labeling it, the other, most important; was that they wished to instill the concept (and did a damn good job of it too) that "love" which was truly "love" could only be the "love" that "god" showed the world by sacrificing his "son" and the "love" that "his son" showed by sacrificing himself.
In other words...in the western mind, the word "love" is almost inseparable from "sacrifice"...bloody, horrible sacrifice.
And thereby perpetuates this word as the only true expression of human desire as well as tying it's believers into a dichotomy of "first love is sweet and "good"" and then comes the awful part.
Mind you, I'm not talking in supposition.
Western/christian/greek educated society had almost no contact with the rest of the world for about 500 years. And during this time, the church had complete control of education. They made damn sure that very few people studied anything more than the bible (this was displayed as recently and quite adequately in the old American West, wherein the only book the children ever read in school, or at home was the bible) (and that's what...the 17-1800's?...now follow that trail back to when Constantine converted Rome to christianity...after which...Rome was sacked and sacked again, until the only remaining power was the church.) And the only literature permitted by the church between those two points in history was the bible...and we all learned "luuuuuuuuuuuuuuuuuuuv"
I say the word "love" is a christian word. I say the use of it has become one of the great sicknesses of our society as it hinders peoples ability to relate to each other as adults or human beings. I can say with certainty I will never say "I love you" to another human being. Unconsciously it tells them, "I want to sacrifice myself to you" and I could go on and on.