tongue (n.) Look up tongue at Dictionary.com
Old English tunge "tongue, organ of speech; speech, a people's language," from Proto-Germanic *tungon (cognates: Old Saxon and Old Norse tunga, Old Frisian tunge, Middle Dutch tonghe, Dutch tong, Old High German zunga, German Zunge, Gothic tuggo), from PIE *dnghwa- (cognates: Latin lingua "tongue, speech, language," from Old Latin dingua; Old Irish tenge, Welsh tafod, Lithuanian liezuvis, Old Church Slavonic jezyku).

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.
tongue (v.) Look up tongue at Dictionary.com
"to touch with the tongue, lick," 1680s, from tongue (n.). Earlier as a verb it meant "drive out by order or reproach" (late 14c.). Related: Tongued; tonguing.