Pursuit of self interest is not selfishness. Life is a game (with high stakes) in which everyone must play to win. Nothing wrong with that. I play to win. Selfishness is cheating at the game. Metaphorically, unselfish people are normal cells. Selfish people are cancer cells. As an activist, I am metaphorically a white blood cell.
Normal cells like me. Cancer cells do not.
it's some much easier when you get to make your own definitions.
Nothing wrong with me defining my terms. You are free to define them differently. I'm all ears.
if you can make the definitions to suite yourself you will never lose a debate.
I'm still waiting for you to define "selfishness". Defining your terms is not a tactic. Every term used in a debate must be clearly defined for the debate to even proceed. Normally, the definition of a word is not controversial as all participants have a common understanding of the term being used. But whenever it becomes apparent that participants are using a term to mean different things, reasonable people of good will will take a moment to negotiate a common definition so that the debate can proceed without confusion.
You have my cancer cell / normal cell metaphore. I think that expresses clearly the distinction that I have in mind regarding self interest versus selfishness. What exactly is your problem with looking at it that way? How do you want to look at "selfishness"?
selfishness is a hijacked word.
It's was originally a synonym for 'looking out for your own self interest'
to use it other wise is 'defining your terms deceptively'
Word history really isn't relevant. (BTW, the word history that I found online does not support your history assertion.) What is relevant is what a word currently means to speakers of the language. Definitions of "selfish" (adjective) found online do not support your assertion:
"(of a person, action, or motive) lacking consideration for others; concerned chiefly with one's own personal profit or pleasure." (Google search)
"devoted to or caring only for oneself; concerned primarily with one's own interests, benefits, welfare, etc., regardless of others. 2. characterized by or manifesting concern or care only for oneself: selfish motives." (dictionary.com)
"1. concerned excessively or exclusively with oneself : seeking or concentrating on one's own advantage, pleasure, or well-being without regard for others 2 : arising from concern with one's own welfare or advantage in disregard of others a selfish act 3 : being an actively replicating repetitive sequence of nucleic acid that serves no known function selfish DNA; also : being genetic material solely concerned with its own replication selfish genes" (https://www.merriam-webster.com/dictionary/selfish)
Word history really isn't relevant
there you go again