A letter opener is the only name that it has; letter opener is a singular, common, compound noun.
bobby joe and bill gates
chaenophryne longiceps
It is often called "A Church Key".
The can opener.
can opener, knife, microwave, toaster, spatula, bottle opener, pot
A pronoun opener introduces a pronoun in a sentence and helps avoid repetition of a noun. For example, in the sentence "Mary went to the store. She bought groceries," "She" is the pronoun opener that refers back to Mary without restating her name.
The name "P38" is a slang term, and not an official name. The original P38 was the German 9mm Pistol (P) made in 1938 (38). The name was borrowed for the C-Ration opener. Still have mine on my dogtags!
It's called good morning
== == how do you use a can opener
This could be an opener.
I-Opener was created in 1999.