Where does “solécisme” come from?

solécisme (French) comes from Latin soloecismus, from Ancient Greek σολοικισμός, from Ancient Greek σόλοικος, from Ancient Greek Σόλοι — Soloi.

Ancestry of “solécisme”, step by step

Step	Language	Word	Meaning
1	Latin	soloecismus	—
2	Ancient Greek	σολοικισμός	solecism
3	Ancient Greek	σόλοικος	speaking incorrectly, using broken Greek; erring...
4	Ancient Greek	Σόλοι	Soloi

solécisme — Etymology, Origin & Word History | Etymology Explorer