I usually thought that you would borrow foreign words for things new that you can hardly transpose in your native language, but how wouldn't the Polish people not have a word for roofs until the Germans came over and borrowed them one? Such an elementary expression, something so ordinary...!
There are old slavic nouns "strzecha" and "poszycie". But their meanings were narrowed down, while "dach" became a general term. "Strzecha" means now a type of roof: "thatched roof"; "poszycie" means a part of the roof: "sheathing". More: https://pl.wikisource.org/wiki/Encyklopedia_staropolska/Dach
Not exactly, according to my OED: The word “(to) thatch” derives from the Old English “theccan”, which by itself has Germanic roots, but does not derive from the New High German “Dach”. The verb “ (to) thatch” is merely related to the verb “decken”, which I would translate as “(to) cover (up)”.
(I also firstly misunderstood your comment and seriously looked up both words you mentioned in my etymological PIE dictionary to wonder where you got your information from, until I reread your comment and saw myself corrected.)
Actually, Catherine was correct about this one. Both thatch and Dach are derived from Proto-Germanic þaką.
I think you ought to cite a discussion of the matter, not just give one source lacking the spelling in question. The essence seems to be that rooves is perhaps still acceptable, but very uncommon: http://english.stackexchange.com/questions/13183/plural-of-roof
It states: „Plural roofs".
„plural roofs or rooves”
„The plural rooves is uncommon and is considered by some to be incorrect, though it is parallel to more common plurals like hooves and staves. However, both roofs and rooves are listed in the Oxford Dictionary of English, 2005 edition.”
70 years a Northern English speaker, I SAY roofs or rooves, whichever sounds well in that particular sentence, and nobody is ever surprised. Roofs aren't a subject I often WRITE about and I must say both spellings look odd to me now. Come to think of it, I'd more likely say rooves if rather romantically ENDING a sentence.