Quirks of English that occur to me when I'm not distracted by television...
Take two nouns that rhyme: "sun" and "fun."
"Sun" generally connotes the star in the sky that casts light on the side of the planet facing it.
"Fun" generally connotes something that elicits enjoyment.
Now append the suffix -ny to both to turn them into adjectives.
"Sunny" generally connotes an adjective form of "sun"; an abundance of sunlight, or having the characteristics of the sun, or being comparable to it.
There's a direct connection between the meanings of the noun and corresponding adjective. If one were asked about a day that featured an abundance of sunlight likely one would use the term "sunny" to describe it.
"Funny" generally connotes something humorous; comedic in intent. (In other contexts it also suggests something that is odd.)
With this noun/adjective pairing, while not utterly disparate in tone, the terms are distinct in connotation. While something funny is often also fun, if one went to a party where one enjoyed one's self, and later one were asked about it, it is less likely one would choose to say it was "funny"; something that happened at the party may have been funny, but the party would be... fun.
However, the sun is always sunny.
Conceivably appending the same suffix to words that are so similar in spelling should result in those corresponding words having similar connections back to their originators, but obviously that is not the case.
Such is the glory of English: There are no rules, only guidelines that may or may not apply--which allows it to be a remarkably adaptive language.
One where sometimes a noun is also an adjective without being modified at all, when this is necessary because the adjective form already has a meaning that doesn't quite match.
Thanks for taking a moment away from TV to read this. Somehow I pulled myself away long enough to get it posted.
Okay. I have to admit: I finished this with the TV on.