Eddy

Etymology

Probably from Old Norse "iða" ("whirlpool, eddy"), or from an Old English prefix "ed-" meaning "back, again." The sense of water turning back on itself runs through both possible roots.

noun · /ED-ee/
A circular movement of water or air running contrary to the main current, forming a small whirlpool.
What it names
The little counter-current swirl behind a rock in a stream — a handy metaphor for pockets that spin against the prevailing flow.
Example
Leaves gathered in a slow eddy at the river’s edge.
Related idea
An eddy is local and rotational; a confluence is the opposite — where two separate flows join into one.