Webster’s Revised Unabridged Dictionary · 1913
Stepping-stone
Step′ping-stone′ (·pĭng·stōn′), n. 1. A stone to raise the feet above the surface of water or mud in walking.
2. Fig.: A means of progress or advancement.
These obstacles his genius had turned into stepping-stones. Macaulay.
That men may rise on stepping-stones Of their dead selves to higher things. Tennyson.