also: うちまたごうやく
double-dealer; fence-sitter; turncoat
A yojijukugo describing a person who opportunistically switches sides or tries to please both parties in a conflict. Literally 'a plaster on the inner thigh', evoking something that sticks to one side then the other. Often used in political or personal contexts.
He's a fence-sitter who always changes his opinion in front of his boss.
あの政治家は内股膏薬と言われ、与党にも野党にもいい顔をする。
That politician is called a double-dealer, trying to stay in favor with both the ruling and opposition parties.
日和見 also means opportunism or fence-sitting, but is more neutral and can refer to a wait-and-see attitude rather than active duplicity.
A similar expression meaning 'double-dealer', literally 'a plaster on both thighs'. 内股膏薬 emphasizes moving between two sides, while 二股膏薬 stresses serving two masters simultaneously.
Standard kanji spelling for this yojijukugo.
Alternate reading; ごうやく is a less common reading of 膏薬.
A yojijukugo combining 内股 (inner thigh) and 膏薬 (plaster, ointment). The image is of a medicinal plaster that is applied to one inner thigh and then shifted to the other, metaphorically describing a person who changes allegiance or opinion to suit the situation. The exact origin is uncertain, but it is a traditional Japanese idiom.