A standard error is the estimated standard deviation $\hat \sigma(\hat\theta)$ of an estimator $\hat\theta$ for a parameter $\theta$.
Why is the estimated standard deviation of the residuals called "residual standard error" (e.g., in the output of R's
summary.lm function) and not "residual standard deviation"? What parameter estimate do we equip with a standard error here?
Do we consider each residual as an estimator for "its" error term and estimate the "pooled" standard error of all these estimators?