early 15c., explanen, "make (something) clear in the mind, to make intelligible," from Latin explanare "to explain, make clear, make plain," etymologically "make level, flatten out," from ex "out" (see ex-) + planus "flat" (from PIE root *pele- (2) "flat; to spread").
The spelling was 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 "to deprive of significance by explanation, nullify or get rid of the apparent import of," generally with an adverse implication, is from 1709.
"to explain, as a man to a woman, in a way that she feels insults or ignores her intelligence and experience in the matter," by 2008, from man (n.) + second element from explain (v.). The form 'splain, as a clip of explain, had been used at least since the 1960s as a colloquialism. Related: Mansplained; mansplaining.
*pelə-, Proto-Indo-European root meaning "flat; to spread."
It forms all or part of: airplane; dysplasia; ectoplasm; effleurage; esplanade; explain; explanation; feldspar; field; flaneur; floor; llano; palm (n.1) "flat of the hand;" palm (n.2) "tropical tree;" palmy; piano; pianoforte; plain; plan; planar; Planaria; plane (n.1) "flat surface;" plane (n.3) "tool for smoothing surfaces;" plane (v.2) "soar, glide on motionless wings;" planet; plani-; planisphere; plano-; -plasia; plasma; plasmid; plasm; -plasm; -plast; plaster; plastic; plastid; -plasty; Polack; Poland; Pole; polka; protoplasm; veldt.
It is the hypothetical source of/evidence for its existence is provided by: Greek plassein "to mold," plasma "something molded or created;" Latin planus "flat, level, even, plain, clear;" Lithuanian plonas "thin;" Celtic *lanon "plain;" Old Church Slavonic polje "flat land, field," Russian polyi "open;" Old English feld, Middle Dutch veld "field."
late 14c., "expound the meaning of, render clear or explicit," from Old French interpreter "explain; translate" (13c.) and directly from Latin interpretari "explain, expound, understand," from interpres "agent, translator," from inter "between" (see inter-) + second element probably from PIE *per- (5) "to traffic in, sell." Related: Interpreted; interpreting.
"meant to explain," 1560s, from past participle stem of Latin interpretari "explain, expound; understand" (see interpret). Interpretive means the same but is considered to be less correctly formed, because -ive adjectives are normally formed on the Latin past participle. Related: Interpretatively.