メンチを切る

• メンチ切(き)る (menchi kiru)

Phrase composed of メンチ (menchi, various possible derivations; see below) + を (o, object particle) + 切る (kiru, “to cut something, to cut across something, to break something; to do something boldly”).

Unknown derivation. メンチ (menchi) on its own generally means mince, as in mincemeat, ground meat. That does not fit this idiom, however.

One explanation is that メンチ (menchi) is an alteration of メンタ, as found in the synonymous Kansai expression メンタを切る (menta o kiru). In this, menta is an alteration of 目の玉 (me no tama, “eyeball”): /me no tama/ → /mentama/ → /menta/. The standard term 目玉 (medama, “eyeball”) is also used metaphorically to mean a glare, a stare; a scolding; compare English hairy eyeball, to eye. In this case, the phrase could be parsed as: menta o kiru → “to boldly eyeball someone” → “to glare in challenge”.

Phonetically, however, there is no clear mechanism for メンタ (menta) to change into メンチ (menchi). A more likely phonetic origin might be 面子 (mentsu, “face, honor”). In this case, the phrase could be parsed as: menchi o kiru → “to cut / break someone else's honor” → “to glare in challenge”.

The derivation may be a combination of the above, where menta may have been influenced by mentsu to become menchi.

• IPA^(key):

メンチを切(き)る • (menchi o kiru) 

1. (idiomatic, chiefly Kansai, slang) to stare or glare in challenge; by extension, to pick a fight
   • 2008, 石原伸司, 逢えてよかった 夜回り組長にココロを預けた少女たちのホンネ, 産経新聞出版, →ISBN, page 20:

     いつものように渋(しぶ)谷(や)センター街(がい)を夜(よ)回(まわ)りしていると、若(わか)い娘(むすめ)が出(で)会(あ)い頭(がしら)にぶつかってきた。「なにメンチ切(き)ってんだよ、オッさん！」 自(じ)分(ぶん)でぶつかっておきながら、男(おとこ)のような言(こと)葉(ば)で因(いん)縁(ねん)を吹(ふ)っかけてくる。

     Itsumo no yō ni Shibuya Sentā-gai o yomawari shite iru to, wakai musume ga deaigashira ni butsukatte kita.“Nani menchi kitte n da yo, ossan!” Jibun de butsukatte okinagara, otoko no yō na kotoba de innen o fukkakete kuru.

     While I was was doing the night rounds through Shibuya Center Street as always, a young girl bumped into me as we passed. “What the hell are you staring at, old man!” Despite her being the one who bumped into me, she tried picking a fight with me with these mannish words.

   • 2013, All About, Inc., editors, Garyū Shingo Taiho / Taima Osen wa Naze Tsuzuku ‎:

     我(が)龍(りゅう)は Ｍ&(エム&)#45;１(ワン) ミドル級(きゅう)王(おう)者(じゃ)のタイトルを保(ほ)持(じ)（逮(たい)捕(ほ)後(ご)の27(にじゅうしち)日(にち)に返(へん)上(じょう)）、Ｋ&(ケイ&)#45;１(ワン)MAX( マックス)を始(はじ)めキック各(かく)団(だん)体(たい)に参(さん)戦(せん)。元(もと)暴(ぼう)走(そう)族(ぞく)という“前(ぜん)歴(れき)”を売(う)りに、金(きん)髪(ぱつ)に染(そ)めたヘアスタイルに、特(とっ)攻(こう)服(ふく)のヤンキースタイルで入(にゅう)場(じょう)、対(たい)戦(せん)前(まえ)には相(あい)手(て)にメンチを切(き)る（にらみ合(あ)う）という不(ふ)良(りょう)パフォーマンスで人(にん)気(き)を博(はく)した名(めい)物(ぶつ)選(せん)手(しゅ)。

     garyū wa Emu-wan midoru-kyū ōja no taitoru o hoji (taiho go no nijūshichi-nichi ni henjō), Kei-wan Makkusu o hajime kikku kakudantai ni sansen. moto bōsōzoku to iu “zenreki” o uri ni, kinpatsu ni someta hea sutairu ni, tokkōfuku no yankī sutairu de nyūjō, taisen mae ni wa aite ni menchi o kiru (niramiau) to iu furyō pafōmansu de ninki o hakushita meibutsu senshu.

     Garyū held the title of M-1 middleweight champion (relinquished on the 27th, after his arrest), and competed in K-1 Max and the other kickboxing leagues. He was a famous competitor who gained popularity for his bad-boy performance, playing up his "past history" as a former biker gang member, coming into the ring wearing his gang regalia with his hair dyed blond, and glaring a challenge at his opponent before a match.

• (Kansai) メンタを切(き)る (menta o kiru)
• (Kantō) 眼(がん)を付(つ)ける (gan o tsukeru)
• (Kantō) 眼(がん)を飛(と)ばす (gan o tobasu)
• (Kantō) 眼(がん)を垂(た)れる (gan o tareru)

• Japanese Slang Dictionary (in Japanese): entry for menchi kiru
• Japanese Slang Dictionary (in Japanese): entry for menta kiru