The headword (extracted from the quotation) is the aorist passive participle, neuter nominative/accusative plural, of the verb xerni/ptomai ("I wash my hands"). As hand-washing was part of a ritual of religious purification before sacrifices and such, the word by extension also means "to purify". See also chi 210 and chi 213.
[1] Greek Anthology 6.156.3 (Theodoridas), a dedication to Nymphs; cf. Gow and Page vol. I (191), vol. II (538-539), and further excerpts at kappa 2191 and pi 2162.
[2] This -- printed by Adler as singular xerni/yato, a slip for xerni/yanto -- is the third person plural, aorist middle/passive indicative, of the same verb, but in an epic form lacking the usual e)- augment; see Hesychius and the scholia to Homer, Iliad 1.449 (where this form of the word appears: web address 1 below).