unfathomable
意味
- 深さが測れない,底なしの
- 不可解な,はかりしれない
語源
英語の原文（Wiktionary）
From un- (prefix meaning ‘not’) + fathom (“to measure the depth of (water); (figurative) to deeply understand (someone or something)”) + -able (suffix forming adjectives denoting things not able or fit to be done).