"the domestic Bos taurus" (commonly meaning the castrated males, used to pull loads or for food), Middle English oxe, from Old English oxa "ox" (plural oxan), from Proto-Germanic *ukhson (source also of 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," (source also of 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."
Also used from late Old English of the wild, undomesticated bovines. The black ox "misfortune, adversity, old age," etc., is by 1540s.
Old English tunge "tongue, organ of speech; speech, a people's language," from Proto-Germanic *tungō (source also of Old Saxon and Old Norse tunga, Old Frisian tunge, Middle Dutch tonghe, Dutch tong, Old High German zunga, German Zunge, Gothic tuggo), from PIE root *dnghu- "tongue."
For substitution of -o- for -u-, see come. The spelling of the ending of the word apparently is a 14c. attempt to indicate proper pronunciation, but the result is "neither etymological nor phonetic, and is only in a very small degree historical" [OED]. In the "knowledge of a foreign language" sense in the Pentecostal miracle, from 1520s. Tongue-tied is first recorded 1520s. To hold (one's) tongue "refrain from speaking" was in Old English. Johnson has tonguepad "A great talker."