I've heard that the word "dog" does not have cognates in any other known language
After your previous question on walk and talk, let's go at it again. First, etymonline (as well as other sources) note that the etymology of dog is still quite foggy. Second, the Old English docga was picked up in other languages, as noted by etymonline, giving the French dogue and the Danish and German dogge (referring to a specific breed).
Third, and most importantly, wiktionary cites the Proto-Germanic dukkōn (“power, strength, muscle”) as the most plausible origin, from which the verb dock also comes. In other languages, the Danish dukke (“doll”) and the German Docke (“small column, bundle, doll, smart girl”) derive from this same root.
As a conclusion, I don't think you can find what you are looking for. There may be words with an etymology so unclear that they might not knowingly be related to any others in known languages, but I don't think you can ever formally exclude the possibility of related cognates.
Tomorrow comes from the Middle English, from the preposition to + morrow. Morrow, which is an archaic or literary word meaning "the following day," comes from Middle English morwe, from Old English morgen.
Morning has origin from Middle English, from morn. Morn comes from the Old English morgen, of Germanic origin.
At the end, both tomorrow and morning comes from the Old English morgen.
Best Answer
Paradise was sometimes spelled with a C in Middle English, though it usually was spelled with S:
The S spelling was favored probably because of the etymology: both of its predecessors, Old French paradis and Latin paradīsus, are spelled with an S.
The time frame makes the reasoning behind the spelling pretty simple: spelling in Middle English wasn’t standardized, and the letters S and C both represent the same sound and were interchanged in many Middle English words. (It’s easy to find examples.) Looking at another word, spice, what is a C in Modern English could be a C, S, or even SC in the word in Middle English.
(Spice is also a word showing that the letters weren’t completely interchangeable. Cp- was not a valid onset spelling even in Middle English so you don’t find it ever spelled cpice or similar.)