Normally defined as...

a simple needlework stitch consisting of a line of small (even? I don't know that it matters) stitches that run in and out through the cloth without overlapping.
Redefined way back as...
The walking stitch. because I tend to do them one at a time.
Considering...
Maybe called a running stitch because it "runs" through the fabric. But really for me, it weaves through or into the fabric.
To be continued...