Isidore of Seville [7th century CE] (Etymologies, Book 12, 4:35): The botrax is so named because it has the face of a frog. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Worms 9.7): Borax, a kind of buffones, has the face of a frog. It is a poisonous animal, as the Experimentator says. Hence, because of the amount of poison it has, when it is touched, it inflates. It fights with a spider and is defeated by it; and this because when the borax has been punctured and it cannot defend itself, it is so inflated by blowing that it cracks in the middle. The bite of borax is very bad and becomes incurable. It has a precious stone on its forehead, for which it is killed. There are two kinds of these stones, one is white and this is better, and the other is brown and black, and has an eye in the middle of it, which it imitates a little by its blue color; but here the brown class is better. This stone is said to cure a person's internal ailments when consumed in food. For the bowels circulate and are taken care of and exit through the lower region. But it must be swallowed whole. Therefore it uses borax, a special herb, when it has an damaged eye, and with this it recovers its sight. Ruta [rue, a herb] kills it. It likes to inhabit wet and damp places. It hates the brightness of the sun and does not allow itself to be easily seen. It walks at night, and this more on roads worn by the footsteps of men; during the day it rests in secret. It flees from the smell of a blooming vine. In parts of Spain the best kind of borax is that which carries the stone which in French we call crapadina [toadstone], but in Latin borax from the animal by which the stone is carried. It is a remedy against poison. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book18.): Botrax is called Rubeta also, and is a manner venemous frogge, & dwelleth both in water and in lande, as Plinius saith lib. 18. cap. 32. And it is sayde, that he chaungeth his skinne in age, & eateth alway certaine hearbes, and kéepeth and holdeth alway venime, & sighteth against the common spinner, and against the spinner that is called Spalangio, and overcommeth their venime and biting by benefise of Plantaine, and his venime is accounted most cold, and stonieth, therefore each member that he toucheth; it maketh lesse feeling, as it were froze, and is a venemous beast, & comforteth therefore himselfe, at each touching: and the more he is touched, the more he swelleth, and as manye speekes as he hath under the wombe, so many manner wise, his venimme is accompted grievous. And he hath eyen, as though they were site shining, and the worse he is, the more burning is his sight, & though he hath cléere eyen, yet he haleth ye light of the Sunne, and séeketh darke places, and flyeth to dennes, when the Sunne riseth, and his beames shineth upon the earth. This Froggs loveth swéete hearbs, and eateth the rootes of them, but in eating, he infecteth and corrupteth both rootes and hearbes. Therefore ofte in gardene in: Rew set, that is venime and enemye to Toades, and to other venemous wormes: for by vertue of Rew, then be chased away, and may not come to other hearbes and rootes that growe therein. The Toade loueth stinking places and dir•ie• and hateth places with good smell and odour: and so it is sayd, that he flyeth out of the vineyard, when the vines begin to bloome, for he maye not suffer nor sustaine theyr good odour and smell. And libro. tricesimo capitulo 4. Plinius speaketh of the Toad, and sayth in this manner. There be right venemous Frogges, that are called Rubetae, and live among briers and bushes, and the more great they be, the worse they be. And some be browne, and some are reddish, and some pale, and soone yeelow, or citrine. And they meane that these wormes Rubetae have double lyver, that one is most venemous, & that other is remedie, & is given in stéed of z-Wikipedia - Triacle against poyson and venime: and for to assay & knowe which is good and which is evill, the liver is throwen into an Ant hill, then the Antes flye and voyd the venemous parte, and desire and choose that other parte, and shall be taken and kept to the use of medicine. And Authours tell wonders of these manner of Frogges as Plinius sayeth, and tell, that in the right side of such a Frogge, is a previe boane, that cooleth same deale séething water, if it be throwen therein: & the vessell may not heate afterwarde, but if the bone be first ta|ken out: and Witches use that boane to love and hate: and they meane also, that the feaver quarlane is healed thereby. And be that worme noiser so venemous, yet by burning he léeseth the mallyce of venymme, and taketh most vertue of medicine: and ashes thereof helpe wonderfullye to recover flesh and skinne that is happelye soft, and to make sadnesse and sinnewes, and to healyng and preservation of wounds, if the ashes be used in over drainer. Looke within De Rana, in litera. - [Batman]