Because

From Middle English bi cause = bi ("by") + cause, modelled on Old French par cause

Full definition of because

1611, Authorized King James Version of Genesis 2:3:And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made.

On account (of), for sake (of).I ruined my life because of you!
Used alone to refuse to provide a full answer a question begun with "why", often taken as an ellipsis of "Because I said so".

1898, Winston Churchill, The Celebrity Chapter 1, I was about to say that I had known the Celebrity from the time he wore kilts. But I see I will have to amend that, because he was not a celebrity then, nor, indeed, did he achieve fame until some time after I left New York for the West.
2013, Katrina G. Claw, Rapid Evolution in Eggs and Sperm, In plants, the ability to recognize self from nonself plays an important role in fertilization, because self-fertilization will result in less diverse offspring than fertilization with pollen from another individual.
1918, W. B. Maxwell, The Mirror and the Lamp Chapter 17, “Perhaps it is because I have been excommunicated. It's absurd, but I feel like the Jackdaw of Rheims.â€ ¶ She winced and bowed her head. Each time that he spoke flippantly of the Church he caused her pain.

I hid myself because I was afraid.
As is known, inferred, or determined from the fact that.
It must be broken, because I pressed the button and nothing happened.
He's not a nice guy, because he yells at people for no reason.
(obsolete) So that, in order that. 15th-17th c.

1621, Robert Burton, The Anatomy of Melancholy, II.3.2:Simon...set the house on fire where he was born, because nobody should point at it.

(for the reason that) therefore, since, for, for that, forthy, for sake, forwhy, as, inasmuch as, âˆµ mathematics symbol