三枚目

The literal sense is a compound of 三 (san, “three”) +‎ 枚 (mai, counter for flat things) +‎ 目 (me, ordinal marker), literally “third sheet, third flat thing”. The idiomatic usage arose from a convention during the Edo Period wherein a kabuki play's comic character (or less commonly, the antagonist) would be listed third on signboards.

• (Tokyo) さんまいめ (Odaka – )
• IPA^(key):

三(さん)枚(まい)目(め) • (sanmaime) 

1. Used other than figuratively or idiomatically: see 三,‎ 枚,‎ 目. (the third sheet or other flat thing)
2. a comic character
3. (by extension) a funny or ridiculous person

• 三(さん)枚(まい)目(め)敵(がたき) (sanmaime-gataki, “a comical antagonist character or role”, see also 敵 (kataki, “antagonist, rival, enemy”))

• 二(に)枚(まい)目(め) (nimaime, “handsome character, male love interest”)
• 二枚目半(にまいめはん) (nimaime-han, “handsome character who is also comical”, literally “second-and-a-half sheet”)