Teach
Old English tǣcan ‘show, present, point out’, of Germanic origin; related to token, from an Indo-European root shared by Greek deiknunai ‘show’, deigma ‘sample’.
wiktionary
From Middle English techen, from Old English tǣċan(“to show, declare, demonstrate; teach, instruct, train; assign, prescribe, direct; warn; persuade”), from Proto-West Germanic *taikijan, from Proto-Germanic *taikijaną(“to show”), from Proto-Indo-European *deyḱ-(“to show”). Cognate with Scots tech, teich(“to teach”), German zeigen(“to show, point out”), zeihen(“accuse, blame”), Gothic 𐌲𐌰𐍄𐌴𐌹𐌷𐌰𐌽( gateihan, “to announce, declare, tell, show, display”), Latin dīcō(“speak, say, tell”), Ancient Greek δείκνυμι(deíknumi, “show, point out, explain, teach”). More at token.
Clipping of teacher
etymonline
teach (v.)
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" (source also of Old High German zihan, German zeihen "to accuse," Gothic ga-teihan "to announce"), from PIE root *deik- "to show, point out." Related to Old English tacen, tacn "sign, mark" (see token). Related: Taught; teaching.
Lemonade Vendor (Edgar Kennedy), enraged: 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.
