show-and-tell (n.)

Middle English sheuen, from Old English sceawian "to look at, see, gaze, behold, observe; inspect, examine; look for, choose," from Proto-Germanic *skauwojanan (source also of Old Saxon skauwon "to look at," Old Frisian skawia, Dutch schouwen, Old High German scouwon "to look at"), from Proto-Germanic root *skau- "behold, look at," from PIE *skou-, variant of root *keu- "to see, observe, perceive."

The causal meaning "let be seen; put in sight, make known" evolved c. 1200 for unknown reasons, seems to be unique to English (German schauen still means "look at"), and in a century displaced the older meaning. The sense of "explain, make clear" is from c. 1300, as the intransitive sense of "be seen, appear."

The spelling shew, popular 18c. and surviving into early 19c., represents an obsolete pronunciation (rhymes with view). The horse-racing sense of "finish third or in the top three" is by 1903, perhaps from an earlier sense in card-playing.

Old English tellan "to reckon, calculate, number, compute; consider, think, esteem, account" (past tense tealde, past participle teald), from Proto-Germanic *taljan "to mention in order" (source also of Old Saxon tellian "tell," Old Norse telja "to count, number; to tell, say," Old Frisian tella "to count; to tell," Middle Dutch and Dutch tellen, Old Saxon talon "to count, reckon," Danish tale "to speak," Old High German zalon, German zählen "to count, reckon"), from PIE root *del- (2) "to count, reckon" (see tale).

Meaning "to narrate, announce, relate" in English is from c. 1000; that of "to make known by speech or writing, announce" is from early 12c. Sense of "to reveal or disclose" is from c. 1400; that of "to act as an informer, to 'peach' " is recorded from 1901. Meaning "to order (someone to do something)" is from 1590s. To tell (someone) off "reprimand" is from 1919.

Original sense in teller and phrase tell time. For sense evolution, compare French conter "to count," raconter "to recount;" Italian contare, Spanish contar "to count, recount, narrate;" German zählen "to count," erzählen "to recount, narrate." Klein also compares Hebrew saphar "he counted," sipper "he told."