Hey Everyone! 
やっと、冬って感じになってきてくれたね。もうそろそろ、衣替えしなくちゃ。
Today, we will be covering…
禿同 （はげどう）
Any guesses on what this one means?
Let’s do a kanji break down.
The state in which the hair that should be there has fallen off and is no longer there. People in that state (bald). A state in which something should be covering a large surface area, but it is not.
It’s not a different thing. It is one thing. The same.
I bet looking at the definition made it even harder to guess what this means.
Is it a word of encouragement used between bald people on the internet? 
Is it a phrase used to express that you are also bald?
No. If you have read my other posts, you probably know that this is probably some sort of typo or the wrong kanji is used purposely.
This word is actually an abbreviation for the phrase 激（はげ）しく同意（どうい）. Which is a phrase used to express that you agree with someone.
Origin 
Like many internet slang, 禿同 originated from 2ちゃんねる. When people agreed with someone, and wanted to emphasize that they really agreed with the, people would reply with 激しく同意, but as you can expect, this was too long to type for some users (that’s 13 letters and a space bar, or two depending on the persons conversion timing). Due to this some people started to type 激同（はげどう）.
So where did the 禿 come from? As you may have expected, the 禿 part was simply a typo, and because some users found it funny, they just went with it and started to use 禿同 instead.
The exact timeline of when this slang started is not known, but it is said that this slang has existed from the early days.
One thing unique about this abbreviation is that this abbreviation birthed a new phrase that used the 禿 kanji, which is 禿げ上がるほど同意, which translates as ‘I agree to the point I start balding (losing hair)’. Makes no sense in both Japanese and English, but it is a phrase that just emphasizes that you REALLY agree with someone.
Most of the time 禿同 is read as はげどう, but because people type はげど when they don’t want to type the extra う to save time, there are people that read and write 禿同 as はげど. So if you see はげど, it is just a shortened version of the abbreviation 禿同.
Examples:
A:夏といったらスイカバーだよね
B:禿同
- A: When it comes to summer, nothing beats suika bar!
B: Strongly agreeA:この実写版のキャスティングは神すぎる。
B:まじ禿同
- A:The people that they cast for this live-action movie are god-tier.
B: Seriously big agreeこのコメント禿同すぎる
- I agree with this comment so much!
Examples with Furigana
A:夏（なつ）といったらスイカバーだよね
B:禿同（はげどう）
- A: When it comes to summer, nothing beats suika bar!
B: Strongly agreeA:この実写版（じっしゃばん）のキャスティングは神（かみ）すぎる。
B:まじ禿同（はげどう）
- A:The people that they cast for this live-action movie are god-tier.
B: Seriously big agreeこのコメント禿同（はげどう）すぎる
- I agree with this comment so much!
Although this word can be used in real life, because it is an older slang, younger people may not understand it. The chances of people understanding might increase on the internet since it is still used by some users and it is one of those internet slang that has been around for a while.
Related slang 
Although this word is not too common anymore, there are other similar words that are still used to this day…as far as I know.
One of the most common synonym is それな. If you have lived in Japan long enough, you probably have heard of it or even have used it yourself!
Although this one does not have a strong nuance like 禿同, it is used when someone agrees with something someone says.
The origins of それな is not known, however, it is said that it either started on 2ちゃんねる or it is simply an abbreviation of the 関西弁 phrase 「ほんまそれな」, which translates to, ‘You’re absolutely right’. This word was originally used on online boards, but it has become more common to use it in daily conversations.
Examples:
A: 今日の作業内容結構エグいよな
B: それな
- A: Today’s work is pretty gnarly isn’t it? (In terms of workload)
B: For realA: 自分が上司だからって、うちらに仕事全部押し付けるの酷くない？
B: それな
- A: Don’t you think it’s unfair that he makes me to all his work just because he is my senpai?
B: For real
Examples with Furigana
A: 今日（きょう）の作業（さぎょう）内容（ないよう）結構（けっこう）エグいよな
B: それな
- A: Today’s work is pretty gnarly isn’t it? (In terms of workload)
B: For realA: 自分（じぶん）が上司（じょうし）だからって、うちらに仕事（しごと）全部（ぜんぶ）押（おい）し付（つ）けるの酷（ひど）くない？
B: それな
- A: Don’t you think it’s unfair that he makes us do all his work just because he is my senpai?
B: For real
As with any other slang, you should only use it when you are talking with people of the same age or friends. Responding with それな to something your senpai has said can sound rude and dismissive.
Another similar word that can be used is ほんそれ. This is an abbreviation of the phrase 本当にそれな, which means that this has a slightly stronger nuance compared to それな.
Examples:
A: あの会社もう終わりだな
B: ほんそれ
- A: That company is done for.
B: For sureA: あいつはどんだけ炎上すりゃ済むんだろう
B: ほんそれ
- A: I wonder how many times he has to blow up before he learns his lesson…
B: For real
Examples with Furigana
A: あの会社（かいしゃ）、もう終（お）わりだな
B: ほんそれ
- A: That company is done for.
B: For sureA: あいつはどんだけ炎上（えんじょう）すりゃ済（す）むんだろう
B: ほんそれ
- A: I wonder how many times he has to blow up before he learns his lesson…
B: For real
Although people do use this in real life, it is more commonly found used on the internet. My assumption for this is because you can express the nuance of ほんそれ by simply saying それな with an energetic voice or an energetic facial expression.
「禿同」を使ったら、「？」ってなるかもだけど、「それな」なら今でも使ってる人多いからみんなも使ってみてね！
ちょっと話変わるけど、最近SNSで面白いもん見つけちゃった。どうやら、名古屋人以外の人には読みにくいらしい！
キットカット買っとかんといかんかったのにあんたが買っとかんかったでいかんかったんだわ
今度ん時はときんときんのえんぴつ持ってかんとかん。てかちゃんと削っとかんとかんって言っとかんとかん。
Fuga
If you missed the previous posts, you can check them out here!
Previous posts
草［乙～スラ（１）］
2ちゃんねる［乙～スラ（２）］
乙［乙～スラ（３）］
ワンチャン［乙～スラ（４）］
炎上［乙～スラ（5）］
飛ぶぞ［乙～スラ（６）］
今北産業［乙～スラ（７）］
特級呪物［乙～スラ（8）］
〇〇構文［乙～スラ（9）］
陰キャ・陽キャ [乙〜スラ（10）]
〇〇ガチャ[乙〜スラ（11）]
自宅警備員[乙〜スラ（12）]
DQN [乙〜スラ（13）]
Semi-useful 2ch Slang［乙～スラ（14）］
FF［乙～スラ（15）］…FF15?
厨二病［乙～スラ（16）］
マジ卍［乙～スラ（17）］
ROM ［乙～スラ（18）］
大きいお友達［乙～スラ（1９）］
フラグ［乙～スラ（２０）］