two-horse carriage
駢 centers on two things paired or aligned side by side, especially two horses drawing a carriage together.
駢 combines 馬 (horse) with 并, which likely contributes both sound and the idea of pairing or joining. The character originally referred to two horses harnessed together.
The left side is a horse 馬, and the right side 并 looks like two lines joined together. Picture two horses paired side by side, pulling a carriage in unison.
For ヘン, imagine a hen sitting between two horses in a carriage: hen -> ヘン, and the two horses are paired together.
elegant classical Chinese prose employing antitheses using four and six-character compound words