I have a dumb question.

Why are there words in German and Latin & Romance languages that are similar even though they are on two different branches of Indo-European? I thought English was pretty much a Germanic language with other stuff thrown in. Could somebody explain this please? Thank you.

speculate=spiegel=speculum

fenestra=finster=defenestrate

Fenster means window in german and welsh, this might be because germanic peoples and celtic britons were still living in mud huts when they came into contact with the Romans. They didn't have a word for a hole in the wall that let light and air in. So perhaps because the Romans introduced them to the idea of a window the Celts copied the name, adapting the term to the local language.

Latin was the common language for communication for centuries in most of Europe so new ideas and concepts were transmitted in that language so a lot of words have latinised forms even if the originating culture wasn't western european.

This might explain why latinate words are common across linguistic boundaries but I am guessing.

our word "car" comes from the Latin "carrus" which is itself a borrowing from the Gaulish "carros," used to distinguish a four-wheeled baggage cart from a two wheeled battle chariot.

during the time when German tribes occupied Rome. Since this was way back beginning in the fifth century AD, the load words underwent the regular German sound changes such as the High German Consonant Shift, hence words like "spiegel" from "speculum."

Much of English Latinate vocabulary comes from Medieval French, which did not undergo Germanic sound shifts, hence "defenestrate" from "fenestra."

Core Germanic vocabulary still makes up the bulk of the English and German lexis, as can be attested by short one-syllable words. cf. Romance "quid"/"qué"/"quoi" with Germanic "what"/"was"/"hva".

Also, there came a point where German stopped adopting Latin words and started making new terms from native Germanic elements, which is why English has "hydrogen," but German has "Wasserstoff."