Although this word sounds similar to “obtuse” (“slow or difficult to understand”), “abstruse” has both a different meaning and a different root word. “Abstruse” is derived from the Latin “abstrusus” (“hidden, put away”), while “obtuse” comes from the Latin “obtustus” (“to beat against”). “Abstruse” references something that has been obscured or is difficult to understand, while “obtuse” refers to someone who has difficulty understanding a clear situation — the root alludes to beating your head against a wall.