the compound "straight-arrow" is a distinctly american english formation from the mid-20th century. it draws metaphorically from the image of an arrow that flies directly and true to its target, without deviation. the "straight" component conveys honesty and directness, while "arrow" implies a focused, unwavering path. thus, the term figuratively describes a person whose moral and behavioral trajectory is similarly direct, honest, and undeviating from conventional standards.

Structure: straight (direct, honest) + arrow (projectile weapon) straight (from middle english streght, from old english streht, past participle of streccan 'to stretch', meaning direct, not crooked). arrow (from old english arwe, earh, meaning a projectile shot from a bow).