Arabian surgeonfish named for the orange, scalpel-shaped patch near its tail

The Arabian surgeonfish (Acanthurus sohal) is named for the two orange, scalpel-shaped markings on the skin of both sides of its body near the pectoral fins and tail. In a recent National Geographic article, Kennedy Warne illustrates the marine life in the waters that surround the Arabian Peninsula: Persian Gulf, Gulf of Oman, Arabian Sea, Gulf of Aden and Red Sea [1]. The bountiful seas include coastal mangrove, coral and sea grass habitats. Warne showcases Arabian surgeonfish on a coral reef in the Red Sea with a glimpse at their combat and grazing behavior. 

The surgery theme is also reflected in the names that have been given to the Arabian surgeonfish in other languages [2]:
French: Chirurgien zébré
German: Rotmeer-Doktorfisch
Spanish: Pez cirujano cebra
Arabian: Fardh and Faridh

The French, German and Spanish terms for surgeon are chirurgien, Chirurg and cirujano, respectively. In German, a physician is called Arzt or Doktor: the latter word appears in Rotmeer-Doktorfisch. Rotmeer means Red Sea. The French and Spanish names focus on the patterns of white stripes, indicated by zébré and cebra for zebra. Unfortunately, my language skills don't go far enough to explain the origin and meaning of the words Fardh or Faridh. Maybe some expert aids with insight?

Keywords: Acanthuridae, Perciformes, ichthyology, comparative linguistics, translation, Arabian world, marine habitats. 

References and more to explore
[1] Kennedy Warne: The Seas of Arabia. National Geographic March 2012, 221 (3), pp.66-89
[byliner.com/kennedy-warne/stories/the-seas-of-arabia].
Note: Warne touches on the battle between different interests of the oil and gas industry,  fishermen and environmentalists, but hints at improving legal protection and marine guardianship taking shape in and between Arabian nation states.
[2] Arabian surgeonfish (Acanthurus sohal) | Factsheet: www.waza.org/en/zoo/choose-a-species/fishes/bony-fishes/acanthurus-sohal.