Learn English – How did “roughly” come to mean approximately

meaning

"Roughly" is used as in "He just pushed me roughly." How did "roughly" then become used as in "They're roughly the same weight."?

Best Answer

Well, you're confusing yourself by starting from a usage that isn't the core meaning of "rough" at all. The core meaning of "rough" is the sense that's to do with physical texture; an irregular, broken surface as opposed to a smooth, flat one. Both meanings you're asking about arise through metaphorical analogy with the physical sense. The "pushed me roughly" derives from the concept of "rough behavior", where behavior stereotyped as associated with lower, working social classes is thought of as "rough" or "coarse", as opposed to upper classes being glorified as "smooth" and "refined". The "roughly the same" sense arises from an analogy of roughness in terms of precision and fit; think of the way two rough surfaces fit together as opposed to the way two smooth surfaces fit together.