It's thought to be derived from the Old English word "būgan", meaning "to bend", which further connects to the Proto-Germanic root "būgō" for "to bow".
Interestingly, the word "buxom" evolved over time to acquire its current meaning of "plump and attractive", specifically referring to a woman's figure.
This change in meaning reflects a shift in societal attitudes towards female beauty, with the emphasis on a yielding and pliable body eventually associating with physical attributes like curves and fullness.