Words/forms avoided because they "look/sound" strange

[Ryanvadar]

An example in English is the avoidance of adding a "-ly" adverb ending to an adjective already ending in "-ly." "He smiled friendlily" is usually rewritten as "He smiled in a friendly way." This is due to the awkward double -ly ending. Dictionaries list some of these forms, but they are not commonly used.

What other examples, in any language, can you think of where certain forms of some words are avoided due to sounding or looking awkward or strange?

[Dormouse559]

Chiot “puppy” has no feminine form in French. I can’t claim causation, but that absence is probably no coincidence because the obvious feminine form, chiotte, happens to be identical to a (separately derived) vulgar word for “outhouse.”

[Khemehekis]

An example in English is the avoidance of adding a "-ly" adverb ending to an adjective already ending in "-ly." "He smiled friendlily" is usually rewritten as "He smiled in a friendly way." This is due to the awkward double -ly ending. Dictionaries list some of these forms, but they are not commonly used.

Er, don't English adjectives that end in -ly usually keep the single -ly ending as adverbs?

https://www.youtube.com/watch?v=T8Xb_7YDroQ

"SoCal is where my mind states/But it's not my state of mind/I'm not as ugly sad as you."

[eldin raigmore]

Er, don't English adjectives that end in -ly usually keep the single -ly ending as adverbs?
https://www.youtube.com/watch?v=T8Xb_7YDroQ
"SoCal is where my mind states/But it's not my state of mind/I'm not as ugly sad as you."

Definitely not usually.
The use of “ugly sad” in the example you quoted is slang, or maybe a “substandard” dialect; at any rate, deprecated.

Edit: Or poetic license!

OTOH, clearly sometimes!
Unless, maybe, it might be better analyzed as a compound adjective; so “ugly” would be another adjective, like “sad”, rather than an adverb.

[Knox Adjacent]

I'm reminded of Old Japanese "adjective" verb classs ending in -si vs -siku.

[lsd]

in French, as in this pretty anthology, it's sometimes better to avoid the feminine gender...