Nowadays, in languages which make a distinction between velar and uvular stops, it's common to use K for the first and Q for the second. This is best-known nowadays from transcriptions of Arabic names, such as Qatar and Kuwait.
Neither Latin nor Greek had a velar-uvular distinction, but they both inherited suitable letters for it (from Phoenician, which did have that contrast). At some point, people evidently started using these letters for their "original" (Phoenician) purpose again.
When did this "original" use start back up again? In other words, when was the first time that the Latin letter Q or the Greek letter Ϙ was used to distinguish a uvular sound from a velar one?