porcelain, make clear, distinguish between
甄 centers on the idea of examining and separating: making something clear by distinguishing it from others, like identifying fine porcelain from ordinary clay.
甄 combines 垔 (likely phonetic, associated with blocking or stopping) and 瓦 (earthenware), originally referring to pottery-making and later extended to the idea of examining and distinguishing, as in refining clay.
The left side 垔 looks like a blocked-off area (西 over 土), and the right side 瓦 is a clay tile. Imagine a potter carefully examining a kiln full of tiles, picking out the finest porcelain from the rest.
For ケン, picture a potter named Ken who can distinguish fine porcelain just by looking: Ken -> ケン, and his keen eye makes everything clear.