Well, where I live, Tuna is also a cactus. Prickly pear is often called tuna. So yeah, tuna (fish) and tuna (fruit) can need disambiguation.

theyre just trying to make it sound right :^)

Given the tvp shenanigans that food manufacturers have tried to pass off and you have to ask? And BTW, dolphin is not a fish

A Czech reporter's name is Jan Tuna. Please keep saying "tuna fish" for his* sake.

* he/him, Jan is a common male name here derived from John, the female counterpart is Jana

"Tuna fish" is a phase used primarily for canned tuna, but not for the live fish or things like tuna steak. It's because when canned tuna was created in the US in the early 1900's people who were not right next to the sea (like the majority of the US) did not know what "tuna" was. Firstly, the word is a of Spanish origin and secondly, its a salt water only fish. So in order to sell this to middle America, which was where most of the consumers were at the time but was also made up of people who have never seen the ocean, they added the word "fish" to show like other tinned fish that was commonly purchased: codfish, bluefish, and whitefish, this is also a fish and that is what you can expect when you open this can.

Americans do love redundancies. e.g Just barely, only just, just a bit, true facts, free gift, end result, advance warning etc.

Tuna was not always popular and when people didn't know what it was it helped people know what they are buying. The US also having a large portion of bilingual people with a Spanish base, this helps it not get confused with cactus fruit (apparently tuna in Spanish)

There's no one single reason, but the top theories:

1. Tuna oil was a thing before "tuna fish". Yes, people could have said "tuna" but they didn't. That's language for you. People say "ATM machine" and "PIN number", too.
2. "Tuna fish" has a slightly sing-song pattern to the stressed/unstressed syllables that probably contributed
3. For whatever reason, "tuna fish" tends to refer to canned tuna, whereas "tuna" can include fresh (or frozen) tuna.

It's… just how language evolves.

I think, however, that "tuna fish" is slowly dying out in favour of just "tuna". As a 50 year old, anecdotally I have seen the usage decrease in my lifetime.

When I hear tuna fish I think stuff in the can. When I hear Tuna I think the filet. I know that’s just me.

In the Netherlands people say koi karper. But koi means karper in Japanese, so basically people say karker karper. It's stupid.

Ever hear of the tuna piano, OOP?

This entire thread is /c/badlinguistics.

I think it's mostly for the dad joke:

You can tune a piano, but you can't tune a fish.

They also love saying Koala Bear (they aren't a bear) and Dingo Dog. No, they're just koalas and dingoes. Americans just seem to like adding words where they aren't necessary. My pet hate is "off of", as in "Take your shoes off of the table!" No, just take them off the table, no need for redundancy.

“Hand me that can of tuna please, I want to make a tuna fish sandwich. “

These words have come out of my mouth.

Yes they’re wrong. But something about the cadence.

If we didn't say that, we wouldn't have the joke about the difference between a piano and a fish.

Colloquially tuna fish refers to the shredded salt brined tins of fish like this:

Which I do think is worth distinguishing from the actual whole pieces of tuna

Same thing as "left-hand side". You're not children anymore, you can just say left side.

Would "left-foot side" make sense? Would it be different from the hand?

Some of you have never eaten tuna cow and it shows

That's "chicken bird for midday lunch," Carl.

It's about conversational cadence. If it was descriptive it would be a hyphenate.