doublet
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.