Where does “asno” come from?

asno (Old Spanish) comes from Latin asinus, from Latin acinus, from Latin acies, from Proto-Indo-European h₂eḱ- — sharp.

Ancestry of “asno”, step by step

Step	Language	Word	Meaning
1	Latin	asinus	a donkey, an ass; an ass, an idiot, a dolt, a...
2	Latin	acinus	a berry, especially the grape; the seed of a...
3	Latin	acies	sharp edge or point; battle line; battle,...
4	Proto-Indo-European	h₂eḱ-	sharp

asno — Etymology, Origin & Word History | Etymology Explorer