Where does “Alyson” come from?

Alyson is an English variant of Old French Alison, itself a diminutive form derived from Old French Aliz.

Ancestry of “Alyson”, step by step

Step	Language	Word	Meaning
1	English	Alison	—
2	Middle English	Alisoun	—
3	Old French	Alison	—
4	Old French	Aliz	—
5	Proto-Basque	-ali	—
6	Old High German	sazzo	—
7	Proto-Germanic	*sittjan	—
8	Proto-Germanic	sitjaną	to sit
9	Proto-Indo-European	sḗd-	—