What is the effect called, where a word loses all its meaning, when repeated over and over in rapid succession?

A platitude? Or baloney bologna.

You mean sorta like when Trump says “Believe me”?

It’s a form of jamais vu, the opposite of deja vu.

Specifically it’s called semantic satiation

I remember as a kid being fascinated by it, repeating my own name until it sounded like a meaningless cluster of sounds.

Semantic saturation or verbal satiation it is repeated on infinitum !

*Fake News” means Trump has gotten caught again with a bad lie. . .

Jinks @Demosthenes I owe you a Coca-Cola !

It becomes gibberish.

Not in succession but same way we tell our partner “I love you” everyday!!