The following extract from “The Guardian” dated January 2018 notes that the neologism “mansplain” has finally entered the OED, after about ten years from its earliest usages. Interenstly the OED notes that the idea behind the term has already become rooted in language.
“Mansplain” also enters the dictionary for the first time.
According to the OED, just 10 years ago the word did not exist, “but the verb (of a man: to explain something needlessly, overbearingly, or condescendingly, especially to a woman, in a manner thought to reveal a patronising or chauvinistic attitude) and the concept it describes now have a firm foothold in the language”.
The earliest known use of mansplain occurs in a pair of comments on the social networking website LiveJournal in August 2008, said the dictionary. The exchange sees a woman “thanking” a male blog commentator for “mansplaining” to her, and he responds asking if it was really “mansplaining”. The term is often misattributed to writer Rebecca Solnit and her book Men Explain Things to Me, though she never used the term in the eponymous essay.
“If those really are the first occurrences of the verb mansplain or the noun mansplaining (in quick succession), then this is a rare example of seeing linguistic creativity in action, and perhaps an insight into what can drive such innovation,” said the dictionary.
Despite its recent coinage, the term is present also in Etymonline:
"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.
It is worth noting that the term “splain” was used mainly with a sarcastic tone and often with a negative connotation well before the term “mansplain” was first used. Merriam-Webster, on this point, notes that:
Sometime in the last 30 years, a subtle shift in its use took place. 'Splain began to be used sarcastically, particularly in Usenet chat rooms, to call out someone for explaining something either without taking the original poster’s comments into consideration or in a extensive and sometimes condescending way.
By 2004, 'splain had gained enough of a negative connotation that when a poster to rec.crafts.woodturning shuts down someone with a sarcastic "could you be a little more splainy about your comment to us," no one jumps in to ask what the excellent splainy means.
From that background the neologism “mansplain” was used from the start with a negative connotation as the the following extract explains:
a portmanteau of man and splaining (short for explaining), the Oxford Dictionary defines mansplaining as “the explanation of something by a man, typically to a woman, in a manner regarded as condescending or patronizing.” It’s the name for the phenomenon that has plagued women for much of history, with most women who I asked exhaling a knowing “Ahhh yes.”
There are multitude reasons why being mansplained to is frustrating, ranging from the fact it might be what you just said repeated back to you in a different way or perhaps the explainer is attempting to coach you on something they are ignorantly unaware that you know a lot about. Whatever the reason, it’s no secret among women that men have been doing this for a very long time and now there’s a word for it.