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depth [depth 词源字典]: depth: [14] Depth is not as old as it looks. Similar nouns, such as length and strength, existed in Old English, but depth, like breadth, is a much later creation. In Old English the nouns denoting ‘quality of being deep’ were dīepe and dēopnes ‘deepness’.
=> deep[depth etymology, depth origin, 英语词源]
adept (adj.): 1690s, "completely skilled" from Latin adeptus "having reached, attained," past participle of adipisci "to come up with, arrive at," figuratively "to attain to, acquire," from ad- "to" (see ad-) + apisci "grasp, attain," related to aptus "fitted" (see apt). Related: Adeptly.
adept (n.): "an expert," especially "one who is skilled in the secrets of anything," 1660s, from Latin adeptus (see adept (adj.)). The Latin adjective was used as a noun in this sense in Medieval Latin among alchemists.
dept.: abbreviation of department, attested from 1869.
depth (n.): late 14c., apparently formed in Middle English on model of length, breadth; from Old English deop "deep" (see deep) + -th (2). Replaced older deopnes "deepness." Though the English word is relatively recent, the formation is in Proto-Germanic, *deupitho-, and corresponds to Old Saxon diupitha, Dutch diepte, Old Norse dypð, Gothic diupiþa.