Eric Frank Russell's "Test Piece" (short story, first contact, free): Don't say it. Or die!

This is a contest story - great anticipation buildup, & a positive conclusion, but key to conclusion is for the reader to find! I wonder how it would look like in a reprint, without contest details of the original publication.

Story summary.

A human ship with 3 crew members has just landed on the alien world of Shaksembender - a followup to the world's discovery message from a scout 300 years ago. A world with hominids who now revere that long forgotten scout as a god. A god who'd asked them to be wary of the coming of men - it will either spell their doom, or will lead to salvation.

And he gave them a test to give to the future human landing party - when put in a certain situation, if the visitors utter two specific words in a sentence, that means doom & they must be immediately destroyed. What are those words? That's for reader to guess.
PS: Rob Slaven thinks the two words are likely to be racially derogatory to blacks of US in 1950s, & that the story is essentially an anti-racism piece.

The crew will meet a reception committee & will successfully pass the test.

Fact sheet.

First published: Other Worlds, March 1951.
Download full text as part of the scans of the magazine it originally appeared in.
Rating: B.
Related: Stories of Eric Frank Russell (annotated list).