teach (v.) Look up teach at Dictionary.com
Old English tæcan (past tense tæhte, past participle tæht) "to show, point out, declare, demonstrate," also "to give instruction, train, assign, direct; warn; persuade," from Proto-Germanic *taikijan "to show" (cognates: Old High German zihan, German zeihen "to accuse," Gothic ga-teihan "to announce"), from PIE *deik- "to show, point out" (see diction). Related to Old English tacen, tacn "sign, mark" (see token). Related: Taught; teaching.
enraged Lemonade Vendor [Edgar Kennedy]: I'll teach you to kick me!
Chico: you don't have to teach me, I know how. [kicks him]
The usual sense of Old English tæcan was "show, declare, warn, persuade" (compare German zeigen "to show," from the same root); while the Old English word for "to teach, instruct, guide" was more commonly læran, source of modern learn and lore.