means A heavy column of timber, steel, or concrete driven deep into the ground to support a structure's foundation, especially over soft or watery soil.

from From 'pile' in its building sense, which traces to Old English 'pīl' meaning a pointed stake or shaft, itself borrowed from Latin 'pilum' — the heavy throwing javelin of the Roman legions. The thread runs from a soldier's spear to a stake hammered into the earth, the common idea being a sharp shaft driven point-first. The '-ing' simply turns the act of driving piles, and the piles themselves, into the everyday word builders use.