rat-race (n.)

also rat race, 1934 in reference to aviation training, from rat (n.) + race (n.1). Rat-run is from 1870 in a literal sense.

A rat race is ... a simple game of "follow the leader" in fighter planes. The leader does everything he can think of — Immelmanns, loops, snap rolls, and turns, always turns, tighter and tighter. [Popular Science, May 1941]

Meaning "competitive struggle" is from 1945.