Louis XIII and his reign set the fashion of wearing wigs. His reason simple enough prematurely balding. Why not wear a wig?? The fashion statement took off and by the middle of the 1600's everyone was getting involved. The wigs would grow bigger as time would go on.
Now I can recall a story that one teacher in my early grades taught me was not that it was seen as esteem but that wig wearing was mandatory. Why you might ask?? Well, according to her it was because of the unclean lifestyle where bugs were abundant and shaving of heads often took place. Real or not I do not know all I know is that I have always recalled that story.
By the time that wig wearing reached the 1800's the wig was a means of showing importance. Wigs were very expensive and only the most prominent could wear the big wigs or "bigwig" The bigger the wig the more important the person. Thus, the term of big head. Are you a big head??
BigWig: Important person