Full of oneself

Full of oneself is an idiom that dates back hundreds of years. An idiom is a commonly used word, group of words, or phrase that has a figurative meaning that is not easily deduced from its literal definition. Often using descriptive imagery or metaphors, common idioms are words and phrases used in the English language […]
from Grammarist
https://grammarist.com/idiom/full-of-oneself/