gigaro.

Unknown. The only attestation in Latin presents it as Gaulish: c. 400, Marcellus Empiricus, De medicamentis, 10:58: Polypum emendat herba proserpinalis, quae Graece draconteum, Gallice gigarus appellatur, vel sucus eius naribus infundatur vel si papyrus inde infecta et spicillo involuta naribus inseratur et postera die educatur; omnes enim morbi radices extrahi eius iniectione manifestum est. A nasal tumour is leeched out by the serpentine, which the Greeks call δρακόντιον (drakóntion), the Gauls gigarus. Either its sap is trickled into the nostrils or a piece of paper is drenched in it and put around a probe which is inserted into the nose and pulled out the next day; it is manifest that all roots of illness can be drawn out by way of this injection. But this is implausible since the word is exclusive to the Tuscany. It appears then that Etruscan was meant instead—indeed in the Dioskurides interpolations 2, 167 it is mentioned that the Θοῦσκοι (Thoûskoi, “Etruscans”) call it γιγάρουν (gigároun), var. γιγάρουμ (gigároum): 40 CE – 90 CE, Dioscorides, De Materia Medica 2.167:^(http://www.poesialatina.it/_ns/Greek/testi/Dioscorides/De_materia_medica_(recensiones_e_codd._Vindob.).html): δρακοντία μικρά· οἱ δὲ ἄρον, οἱ δὲ ἀρίς, οἱ δὲ ἔπαρσις, οἱ δὲ παρνοπόγονον, οἱ δὲ κυνό‹ζ›ολον, οἱ δὲ φοινίκεον, οἱ δὲ ὀνοκεφάλιον, οἱ δὲ ἐφιάλτιον, Αἰγύπτιοι ἐβρών, οἱ δὲ ἐρυθμόν, Ῥωμαῖοι βῆτα λεπορίνα, Θοῦσκοι γιγάρουμ, Ἰστριανοὶ λάγμα, Δάκοι κουριοννηκούμ, Ἄφροι ἀτειρνοιχλάμ, Σύροι λοῦφαν. drakontía mikrá; hoi dè áron, hoi dè arís, hoi dè éparsis, hoi dè parnopógonon, hoi dè kunó‹z›olon, hoi dè phoiníkeon, hoi dè onokephálion, hoi dè ephiáltion, Aigúptioi ebrṓn, hoi dè eruthmón, Rhōmaîoi bêta leporína, Thoûskoi gigároum, Istrianoì lágma, Dákoi kourionnēkoúm, Áphroi ateirnoikhlám, Súroi loûphan. (please add an English translation of this quotation) Another source proposes instead a derivation, through the form giaro, from Latin arum, from Ancient Greek ἄρον (áron), with around the same meaning.