I don’t understand what you are saying here.
The word “marriage” isn’t only a religious word and it isn’t defined by one religion. It also means a union of many different varieties.
As far as marriage between two people go…according to the dictionary and encyclopedia, the word “marriage” first appeared in 1250–1300 AD/CE, deriving from middle English.
Since approx 1400, the word has been applied to mean any close union or blending of any two things.
And the institution of marriage pre-dates recorded history.
So neither the *act *of getting married nor the word “marriage” finds their origin only in the Judeo-Christian religion, or any other religion for that matter.
So no one is “hijacking” the term from anyone.
Well, actually…wait.
Merriam Webster defines marriage as:
(1) : the state of being united to a person of the opposite sex as husband or wife in a consensual and contractual relationship recognized by law
(2) : the state of being united to a person of the same sex in a relationship like that of a traditional marriage <same-sex marriage>
So I guess you could say that if we define it only as between male-female, then we’d be hijacking the term from Merriam-Webster…