The word “man” may have roots in old Indo-European terms for “to think,” and the word man may have been meant to mean “one who thinks.” Some linguists disagree on these origins.
Before “man” was used, Old English used the words wer and wif to distinguish the sexes (wer being man, wif being woman). That’s why “werewolf” basically means “man wolf.” But the word “man” replaced wer around the late 13th century
Interestingly, up until about 1000 years ago, the word “man” was originally gender neutral, so that’s a recent development
- And you might be interested in this study about Sexism in Language: http://www.jllonline.co.uk/journal/5_1/5LingLei.pdf