on foot

From Middle English on fote, from Old English on fōte (“on foot”), equivalent to on +‎ foot.

on foot

1. On one's feet; walking, jogging or running but not in a vehicle or on the back of an animal. [from 10th c.]

   The pub's not far: let's go on foot.

   • 1949 November and December, “Notes and News: Festiniog and Welsh Highland Railways”, in Railway Magazine, page 408:

     At the same time, the encroachment of vegetation proceeds apace, and broom and brambles have already made portions of the line impassable, even on foot.

2. (now rare, chiefly hunting) On the move; astir. [from 14th c.]
3. In progress or in preparation; active, in operation. [from 16th c.]
   • 1789, John Moore, Zeluco, Valancourt, published 2008, page 113:

     [W]ithin a short time it was generally believed at Naples, that a treaty of marriage was on foot between Zeluco and the young lady in question […] .

• (walking, jogging or running): by foot, afoot