. English /f/ is adapted as [ph] or [hw] into Korean. The adaptation of English /f/ into [hw] in Korean has been considered a historical relic from Japanese adaptation. This paper makes four claims by investigating loanword corpora. First, [hw] is a valid adaptation word-initially even for words newly adapted into Korean very recently. Second, the adaptation of words can change over time, even after they have been lexicalized, to reflect source faithfulness, e.g., a medial /f/E-> [hw]K adaptation in 1937 might become /f/E-> [ph]K in current Korean. Third, this happens because medial [hw] is subject to lenition in Korean, and the form is “re-borrowed” to preserve the segment. Fourth, an account within a Maximum Entropy model better predicts the observed frequency of loanword variants than the classical Optimality Theory-based analysis. This study suggests that perceptual similarity between the source and borrowing sounds better explains the asymmetrical adaptation of English /f/ than phonological correspondences in loanword adaptation.