Growing Knowledge

In space, after leaving Talwin, Ydwyr mentions "Aycharaych" which means nothing to Dominic Flandry who, if he had been more experienced, would have concealed his ignorance in the hope of learning more.

Later, back on Talwin, Flandry spots an exotic being, inquires of his Merseian informant and begins to learn about the planet, Chereion.

Notes:

We know of three occasions when Flandry is on Talwin, the third time in conversation with Aycharaych;

retroactively, we realize that that Chereionite spotted on Talwin must have been Aycharaych.

Finally, Flandry meets Aycharaych of Chereion at Betelgeuse. This was the earliest published of these instalments. However, building a future history series involved constructing an elaborate set of prequels, as we see here.