汉德森 transliterates the English surname Henderson. The standard pattern:
汉 (hàn) for 'Hen-',
德 (dé) for '-der-',
森 (sēn) for '-son'. The
森 (forest) ending is a near-universal Mandarin rendering of English '-son' (compare
杰克逊 Jackson,
约翰逊 Johnson,
威尔逊 Wilson — though those use
逊 instead of
森).