Selfishness

Etymology

A relatively late English coinage — "self" + "-ish" + "-ness" — recorded from the mid-1600s and reportedly minted by Presbyterian writers who needed a word for the sin of self-preference. Before it, English had no plain noun for the trait.

noun · /SEL-fish-nis/
Concern for one’s own advantage without regard for others.
What it names
The ordinary, everyday vice of putting oneself first by default — the water we swim in, worth naming so it can be seen.
Example
It was a small selfishness — the last seat, the better slice — but it added up over the years.
Related idea
Egotism is inflated self-importance in thought and talk; selfishness is self-preference in action. One is about how you see yourself, the other about how you treat others.