Echika is a new underground shopping area around the Omotesando subway station. As Jean Snow has pointed out, the name Echika “is probably an attempt at a pun-tastic combination of the Japanese words eki (station) and chika (underground), but mostly making one think of echi, with its sexual connotations.”
I couldn’t find any information about it in English online, but the explanation for the bunny mascot on the What’s Echika page at the official site is kind of interesting. It relates to the White Rabbit that was Alice’s guide after she fell down from mundane above-ground world through the rabbit hole and into the Wonderland below.
But if you go there expecting to encounter a wonderland, you’ll probably be a bit disappointed. It’s just 26 smallish shops in 5 different areas. Mostly food places, with a few shops (stalls?) selling accessories and “supplements” or some damn thing. But to make the areas more wonderful, they all have French names: Espace Japon, Marché de Metro, Espace Beauté, Espace Mode, Espace Appétit.