Phrase to describe someone who’s quiet on the outside but loud on the inside?

What’s a phrase for someone who hides their feelings but knows how to express them? Usually they do it online or by themselves or with just a couple people. Is there an idiom for that? The only one I can think of “is business up front, party in the back.” But I found out that’s a type of haircut.

Does anyone have any insight?

I don't know for sure, but that best describes me...I have been called "eccentric" before which seems to be similar...

A ticking time bomb.

A strong silent type.

The saying 'still waters run deep' came to mind. Here's something written about it on the internet. I'm probably waffling off topic here but I thought it was quite interesting.


To describe someone with the phrase still waters run deep may mean that the person may appear calm on the outside, but be seething with passion underneath their cool exterior. Still waters run deep may also mean the person appears to have nothing interesting to say, but in fact, is a deep thinker and has many ideas. The proverb still waters run deep may be traced to Rome in the first century. In Quintus Rufus Curtius’ work Alexander the Great, he writes: “altissima quaeque flumina minimo sono labi”, which translates as “the deepest rivers flow with the least sound”. The proverb was written as an Aesop fable that was included in the collection published by Roger L’Estrange in the 1690s as A Country-man and a River.

''Seething with passion."

I also like ‘measured’ as in a measured response.

I like "business up front, party in the back" like you said. I never heard of that haircut. I wonder what it looks like.

I think it’s a mullet.

....

When I was talking to my therapist about being loud on the inside I said “you know it’s like that saying, business in the front, party in the back.” I couldn’t quite read her expression but she nodded so I guess it worked out.

bet she thought about that phrase afterwards...

I googled. Yep, it's a mullet. Some of the ole boys in my area still wear mullets. I thought it was dumb looking back in the day. Still dumb looking.

I heard someone say about the Amish one time

“Church in the front, party in the back.”

Because sometimes they do stuff against their religion to be rebellious. And not just the teenagers either.

MountainDewed, I've heard that phrase too.