explainyoudaoicibaDictYouDict[explain 词源字典]
explain: [15] To explain a matter is literally to ‘make it plain’. The word comes from Latin explānāre, a compound verb formed from the intensive prefix ex- and the adjective plānus ‘flat’ (source of English plain). This originally meant ‘flatten out, make smooth’, but the metaphorical sense ‘make clear’ soon took over, and accompanied the verb into English (although in the 16th and 17th centuries a few scholars attempted to revive the literal sense: ‘He must calm and explain his forehead’, Sir Thomas Chalenor, translation of Desiderus Erasmus’ Praise of Folly 1549).
=> esplanade, plain[explain etymology, explain origin, 英语词源]
explain (v.)youdaoicibaDictYouDict
early 15c., from Latin explanare "to explain, make clear, make plain" (see explanation). Originally explane, spelling altered by influence of plain. Also see plane (v.2). In 17c., occasionally used more literally, of the unfolding of material things: Evelyn has buds that "explain into leaves" ["Sylva, or, A discourse of forest-trees, and the propagation of timber in His Majesties dominions," 1664]. Related: Explained; explaining; explains. To explain (something) away is from 1709.