(by reduplication) from an unused root (meaning to belch forth); an inflammatory pustule (as eruption) -- blains.
H76. ababuah
אֲבַעְבֻּעֹת noun feminine plural blisters, boils (אֲבַעְבּוּעְיָן ᵑ7; compare בֶּעְבַּע ᵑ7, Late Hebrew בּוּעָה בַּעְבּוּעַ, Syriac ) Exodus 9:9 אֲבַעְבֻּעֹת מֹּרֵחַ שְׁחִין, compare 9:10.
בוץ so Thes, better ביץ (compare Arabic surpass in whiteness; whiteness).