Phonetic:
汉 (hàn, 'Han / Chinese') for 'Ham-',
姆 (mǔ, 'nurse/auntie') for '-m-' —
姆 is Chinese's go-to syllable for foreign '-m'/'-mi'/'-ma' (cf.
姆斯特 in
阿姆斯特丹 'Amsterdam').
顿 (dùn, 'pause') is the standard syllable for the English '-ton' suffix (cf.
华盛顿 'Washington').