doublet
/ˈdʌblɪt; `dʌblɪt/ n
1 (formerly) short close-fitting jacket worn by men, with or without sleeves （旧时）男用紧身上衣或背心.
2 either of a pair of similar things, esp one of two words with the same origin but a different form or meaning, eg hospital/hostel 一对类似的东西中的一个; （尤指同源异形或异义的）双式词, 如hospital/hostel.