Where does “ronha” come from?

ronha (Portuguese) comes from Latin aranea, from Ancient Greek ἀράχνη — spider; a spider's web.

Ancestry of “ronha”, step by step

Step	Language	Word	Meaning
1	Latin	aranea	spider; spider's web, cobweb; threads similar to...
2	Ancient Greek	ἀράχνη	spider; a spider's web