O.E.
tæcan (past tense and pp.
tæhte) "to show, point out," also "to give instruction," from P.Gmc.
*taikijanan (cf. O.H.G.
zihan, Ger.
zeihen "to accuse," Goth.
ga-teihan "to announce"), from PIE
*deik- "to show, point out" (see
diction). Related to O.E.
tacen, tacn "sign, mark" (see
token). O.E.
tæcan had more usually a sense of "show, declare, warn, persuade" (cf. Ger.
zeigen "to show," from the same root); while the O.E. word for "to teach, instruct, guide" was more commonly
læran, source of modern
learn and
lore.
Teacher "one who teaches" emerged c.1300; it was used earlier in a sense of "index finger" (c.1290).
[thach] 
