Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium.
Note: The other elements may or may not be actual metals in the true sense of their defintion.
But why did astronomers use such a term as
metallicity? What is the history and cause behind coining such a term that may be (or rather actually is being) confused with
metal-content of that celestial object ?
Is there any scientific objective or explanation to this? I do not believe it is just a random acceptance, but perhaps there is a not-so-solid motive behind doing this. If there is, what is it?