Origin: 1480–90; earlier hach-boon (with spurious h-); (h)ach var. by misdivision as an (h)ach(e) of a nache rump < MF < VL *natica, fem. of *naticus of the rump, equiv. to L nati(s) rump, nates+ -cus adj. suffix
[Alteration (influenced by aitch) of Middle English hach-boon, from an hach-boon, an aitchbone, alteration of a nachebon : nache, buttock (from Old French, from Late Latin naticās, accusative pl. of natica, buttock, from Latin natis) + bon, bone (from Old English bān).]