Japanese word “omoshiroi” means “interesting” .
“Omo” means “face” and “Shiroi” means “white”. According to a Japanese myth, when Goddess of Sun went into a cave, the world became dark. Many people gathered in front of the cave and started to dance to attract the attention of Goddess. As she came out of the cave to see what was going on, the world became bright and everyone’s face changed from dark to white ＝bright. The people shouted, “Great! Everyone face has become bright.”
So the things which make people’s faces white or bright is “omoshiroi”in Japanese = “interesting”.
その昔、天照大神が天の岩戸にお隠れになったとき、この世が真っ暗になった。
困った人々が岩戸の前に集まり音楽に合わせて舞を舞って神様の気を引こうとした。(これがお神楽の始まりと言われている) 神様が出て来られたとき、世が明るくなって人々の顔も明るくなったので人々は歓喜して「顔が白い」すなわち「面白い」と叫んだと言うことです。
ということで「面白い」は人々の顔を明るくする物事を描写する言葉となった。