I actually know what this refers to. It's a speech experiment in which people associate certain vowel sounds with certain shapes. Bouba (boba in the comic) is associated to having a rounder, blob-like shape. Kiki is associated with a sharper, angular shape. The experiment crosses languages and cultures and generally holds across them all. It tells us some interesting things about the roots of human language and the brain's associative properties to physical attributes in the descriptors we use in language. This comic is very niche for sure. I was surprised to see such and obscure thing and more surprised that I knew exactly what it was referring to. Stonetoss threw us a real riddle here.

Sorry for the (((wikipedia))) link... https://en.wikipedia.org/wiki/Bouba/kiki_effect

I don't get it.

I'll ask: what the fuck is a kiki?