In English when you talk about scientific, technical, legal or medical topics, you tend to use a lot more words of Latin, Greek and French origin. However in everyday conversation words of Anglo-Saxon and Old Norse origin are much more common. Therefore you could say that English has two distinct registers – a higher register used in academic and other formal settings, and a lower register used elsewhere. New scientific terms are usually coined from Latin and/or Greek roots. Mixing the registers or using one where the other would normal be used can a source of humour.
In other languages, such as German, new words tend to be coined from native roots. This gives you words like Wasserstoff (water material/stuff), for hydrogen, Sauerstoff (sour/acidic stuff) for oxygen, and Stickstoff (close/stuffy stuff) for nitrogen.
According to this post, such words can sound funny to English speakers because they are made from words similar to lower register English ones which are not normally associated with serious vocabulary like this.
There have been suggestions and proposals that new English be coined from native Old English / Anglo-Saxon roots, none of which have really caught on. For example, in a text on atomic theory, Uncleftish Beholding by Poul Anderson, almost all the words are of Anglo-Saxon origin and there are many newly coined words, including beholding for theory, waterstuff for oxygen, ymirstuff for uranium, bulkbits for molecules, and worldken for physics.
There is even a group of people called The Anglish Moot, who aim to create a version of English free of loanwords from other languages.