Perhaps Wikipedia by way of the old QNX FAQ? https://web.archive.org/web/20080424102623/https://www.bitct...

“In the early 80's they began work on a small message passing kernel based OS that had some user interface similarities to UNIX.”

“They called their product QUNIX, reportedly because it was a "Quick UNIX". They named their company Quantum Software Systems Limited. The QUNIX name lasted a year or two until they received notice from AT&T; that a change would be appropriate. Always ready for a challenge, they changed the spelling to QNX® without changing the pronunciation.”