Words related to echo
"oral instruction, catechism," 1753, from Latinized form of Greek katekhesis "instruction by word of mouth," from katekhein "to instruct orally," originally "to resound" (with sense evolution via "to sound (something) in someone's ear" to "to teach by word of mouth"). From kata "down" (in this case, "thoroughly") + ekhein "to sound, ring," from ekhe "sound," from PIE *(s)wagh- "to resound" (see echo (n.)).
digraph used in Old French for the "tsh" sound. In some French dialects, including that of Paris (but not that of Picardy), Latin ca- became French "tsha." This was introduced to English after the Norman Conquest, in words borrowed from Old French such as chaste, charity, chief (adj.). Under French influence, -ch- also was inserted into Anglo-Saxon words that had the same sound (such as bleach, chest, church) which in Old English still was written with a simple -c-, and into those that had formerly been spelled with a -c- and pronounced "k" such as chin and much.
It turns up as well in words from classical languages (chaos, echo, etc.). Most uses of -ch- in Roman Latin were in words from Greek, which in Greek would be pronounced correctly as /k/ + /h/, as in modern blockhead, but most Romans would have said merely /k/, and this was the regular pronunciation in English. Before c. 1500 such words were regularly spelled with a -c- (Crist, cronicle, scoole), but Modern English has preserved or restored the etymological spelling in most of them (chemical, chorus, monarch).
Sometimes ch- is written to keep -c- hard before a front vowel, as still in modern Italian. In some languages (Welsh, Spanish, Czech) ch- can be treated as a separate letter and words in it are alphabetized after -c- (or, in Czech and Slovak, after -h-). The sound also is heard in words from more distant languages (as in cheetah, chintz), and the digraph also is used to represent the sound in Scottish loch.
Onomatopoeia, in addition to its awkwardness, has neither associative nor etymological application to words imitating sounds. It means word-making or word-coining and is strictly as applicable to Comte's altruisme as to cuckoo. Echoism suggests the echoing of a sound heard, and has the useful derivatives echoist, echoize, and echoic instead of onomatopoetic, which is not only unmanageable, but when applied to words like cuckoo, crack, erroneous; it is the voice of the cuckoo, the sharp sound of breaking, which are onomatopoetic or word-creating, not the echoic words which they create. [James A.H. Murray, Philological Society president's annual address, 1880]