Taboo pieces?

I’ve been studying various chess terms, and on a couple of games I’ve seen a piece described as taboo, and am unsure what this means. For example, on a game study the author said the white queen was taboo when it looked close enough to the black king to threaten checkmate. I can’t seem to find a specific definition anywhere though for what specifically makes a piece taboo and wonder where this term came from, or is it an outdated or casual term that’s not really used anymore?

I would take it to mean that the piece can't be taken, because if it was, the player making the capture is opened up to mate or a larger loss of material.

Thanks MS that actually seems to fit what I saw just right. Appreciate your answer.