Japanese idiomatic expression with Japanese sword #1

There are some idiomatic expressions in the Japanese conversation referring to the Japanese swords. There seems to be most Japanese people even do not know those etymologies since a Japanese sword is no longer close to their daily life. I am going to introduce some Japanese expressions coming from the Japanese swords.

The first one is “shinogi wo kezuru（しのぎを削る）” = shave a shinogi

First of all, what is shinogi（鎬）?