plural of ox, it is the only true continuous survival in Modern English of the Old English weak plural. OED reports oxes occurs 14c.-16c., "but has not survived."
Old English oxa "ox" (plural oxan), from Proto-Germanic *ukhson (cf. Old Norse oxi, Old Frisian oxa, Middle Dutch osse, Old Saxon, Old High German ohso, German Ochse, Gothic auhsa), from PIE *uks-en- "male animal," (cf. Welsh ych "ox," Middle Irish oss "stag," Sanskrit uksa, Avestan uxshan- "ox, bull"), said to be from root *uks- "to sprinkle," related to *ugw- "wet, moist." The animal word, then, is literally "besprinkler."
Heb. bakar, "cattle;" "neat cattle", (Gen. 12:16; 34:28; Job 1:3, 14; 42:12, etc.); not to be muzzled when treading the corn (Deut. 25:4). Referred to by our Lord in his reproof to the Pharisees (Luke 13:15; 14:5).