Why are pot-holes called pot-holes?

Solution 1:

According to Etymonline,

pothole (n.) 1826, originally a geological feature in glaciers and gravel beds, from Middle English pot "a deep hole for a mine, or from peat-digging" (late 14c.), now generally obsolete, but preserved in Scotland and northern England dialect… Applied to a hole in a road from 1909.

Oxford suggests that the M.E. pot meaning "pit" may be of Scandinavian origin.

The French nid-de-poule (hen’s nest) is much more colorful.

Solution 2:

According to pothole.info, the holes in roads were named in analogy to "pot-holes" where a river or stream has cut a similar hole in the bed, about the size and shape of a cooking pot.

Solution 3:

According to the OED, the origin of pot in this sense is uncertain. It may be from the Old Swedish potter, meaning 'a hole, well or abyss'.