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.[1][2] 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): [mẽ̞ɴt͡ɕi o̞ kiɾ̠ɯᵝ]

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 [Shingo Garyū Arrest: Why Does Marijuana Pollution Continue?]‎:

     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