While the exact reason for the naming of the genus is unknown, the name has been theorized to have been derived from Ancient Greek πᾶς (pâs; "all") and μᾰχητής, (makhētḗs; "warrior", "fighter"). It also coincides with the name of Pasimachus, a cavalry commander mentioned in Hellenica. The reason for this naming could be due to the genus' large mandibles and carnivory.
↑"Genus Pasimachus". BugGuide.net. Retrieved April 25, 2023. The etymology of Pasimachus: "Probably from the Greek pasi (the whole, all, very, by extension universal) and machetes (warrior, fighter) contracted [masculine]." (GBIF) In addition, note that Pasimachus was a Dorian cavalry commander of the Peloponnesian War mentioned in Xenophon's Hellenica.