ambivert (n.)

"person exhibiting features of an extrovert and an introvert," coined by Kimball Young in "Source Book for Social Psychology" (1927), from ambi- "about, around" + -vert (as in earlier introvert), which is ultimately from Latin vertere "to turn," from PIE root *wer- (2) "to turn, bend" (see versus). Related: Ambiversion.