ブラウザの設定でJava Scriptの使用を有効にしてご利用ください。
出典:Wiktionary
head + scratching, from the fact that many people scratch the side of their head when confused.
head-scratching (comparative more head-scratching, superlative most head-scratching)
head-scratching (複数形 head-scratchings)
head-scratching