Where does “guernier” come from?

guernier (Old French) comes from Old French grenier, from Latin grānārium, from Latin grānum, from Proto-Italic grānom, from Proto-Indo-European ǵr̥h₂nóm, from Proto-Indo-European ǵr̥h₂nós, from Proto-Indo-European ǵerh₂- — to grow old, to mature.

Ancestry of “guernier”, step by step

guernier traces back through two separate lines of ancestry.

via Old French grenier

Step	Language	Word	Meaning
1	Old French	grenier	—
2	Latin	grānārium	granary
3	Latin	grānum	grain, seed, small kernel
4	Proto-Italic	grānom	grain
5	Proto-Indo-European	ǵr̥h₂nóm	grain
6	Proto-Indo-European	ǵr̥h₂nós	matured, grown old
7	Proto-Indo-European	ǵerh₂-	to grow old, to mature

via Latin granarium

Step	Language	Word	Meaning
1	Latin	granarium	granary
2	Latin	-arium	Used to form nouns denoting a "place where things...
3	Latin	-arius	Used to form adjectives from nouns or numerals;...
4	Proto-Indo-European	-yós	Creates adjectives from noun or verb stems

Every word from Proto-Indo-European ǵerh₂- →Every word from Proto-Indo-European ǵr̥h₂nós →Every word from Proto-Indo-European ǵr̥h₂nóm →