The story
From Korolev + cross. From the cross shape formed by the 4 boosters of the R-7/Soyuz family of rockets as they separate from the core, and the name of the rocket's chief designer, Sergei Korolev.
Etymology from Wiktionary, CC BY-SA 4.0.
Korolev cross
Today it means: A rocket booster separation maneuver, especially that of the Soyuz rocket family, where four side boosters are ejected at the same time in four directions 90° offset from each other, forming a cross shape. Full definition →