Chambering first occurance in the KJV is in Genesis 43:30.
(Genesis 43:30 [KJV]) And Joseph made haste; for his bowels did yearn upon his brother: and he sought where to weep; and he entered into his chamber, and wept there.
This shows that chambering is about being in your chamber.
(Judges 15:1 [KJV]) But it came to pass within a while after, in the time of wheat harvest, that Samson visited his wife with a kid; and he said, I will go in to my wife into the chamber. But her father would not suffer him to go in.
Chambering can also mean lying in bed. For example with your wife (Judges 15:1).