I understand where you are coming from but let us dig deeper into the language itself. Sinister in Latin means, "left hand". Also in French the word for left hand is guache which is "vulgar".

sinistersinister

adjective
sin·is·ter ˈsi-nə-stər archaic sə-ˈni-
Synonyms of sinister
1 : singularly evil or productive of evil
2 : accompanied by or leading to disaster
3 : presaging ill fortune or trouble
4a : of, relating to, or situated to the left or on the left side of something
especially : being or relating to the side of a heraldic shield at the left of the person bearing it
b: of ill omen by reason of being on the left
5 archaic : unfavorable, unlucky
6 archaic : fraudulent
sinisterly adverb
sinisterness noun

-- https://www.merriam-webster.com/dictionary/sinister

##gauche

adjective
ˈgōsh
sometimes gaucher; sometimes gauchest
Synonyms of gauche
1a: lacking social experience or grace
also : not tactful : crude
it would be gauche to mention the subject
b: crudely made or done
a gauche turn of phrase
2: not planar
gauche conformation of molecules
gauchely adverb
gaucheness noun

-- https://www.merriam-webster.com/dictionary/gauche

French Left Hand: https://www.collinsdictionary.com/dictionary/english-french/left-hand

Sinister etymology: https://www.etymonline.com/word/sinister