What is the meaning of GY-X nomenclature in chips?
It's a model number for the breakout board. It doesn't have any deeper meaning.

A quick search finds a number of other sensor breakout boards with similar names, e.g.


GY-21, a humidity sensor
GY-31, a color sensor
GY-52, an accelerometer/gyroscope
GY-291, another accelerometer


Most of these appear to be ad-hoc names used by small Chinese manufacturers. If you need to describe these boards, make sure to reference the name of the part on the board (e.g, "MS5611"), as it will be easier for others to find than the specific breakout you used.