Even if English is your first language - sometimes questions come up at work that you need to check the correct work terminology for. Calling something a nonsense term at home can work - calling it the same nonsense term at work may get a laugh & the correct term once - but the fourth or fifth time, it won't be a laugh, it'll be a comment about "learn the correct terminology" from a coworker or boss.
Insurance, car repair, computers, dentists, and other work fields all have one thing in common - there are terms that they use in a particular way that other work fields either don't have those terms or use similar words to mean something completely different. An example might be the word "filter" - a "filter" for a computer programmer would probably written into some software, a "filter" for a photographer is a physical item for the camera OR possibly a software choice when editing raw photos, and a "filter" at a car repair place may be for oil, fuel, air to the engine or for the heating & A/C to the cabin.
Other places may use words that just don't turn up in your average conversation unless you're discussing that subject ("Subrogation" is an insurance term that I don't recall using except to an insurance agent or at least when talking about an insurance claim).
"Claimant" has a slightly different, but related meaning in insurance as it does in law. But the other party in a claim is not called the "defendant" as they might be in a legal matter - they are usually called the "insured" by the company that they have bought their insurance from.
Use the wrong term (or one that is almost right in the wrong office) and you'll still have a miscommunication.
For someone who is working in a second language - the specific vocabulary used for that job may be almost like having to learn a third language! I know that in various careers, I've had to learn enough new terms to get the idea that I was no longer speaking the "English" that I knew growing up!