+ ass , from the slang expression hat , thus, wearing the ass as a hat. The term is extended to people who are clueless or bumbling, who don't understand what is going on.
have one's head up one's ass
asshat ( plural ) asshats
An ( Canada, US , derogatory , slang , vulgar ) obnoxiously ignorant person; a fool.
1998 July 23, T..., “Re: GREEN RIVER NARROWS, NC: ALL PUTINS CLOSED!!”, in rec.boats.paddle (  Usenet), retrieved 2018-10-04, message-ID <firstname.lastname@example.org>: the same connotations as "FUCKWITS." for less extreme cases i suggest ASSHATS
1999 July 23, madge, “California Hustle,”, in alt.fan.erik (  Usenet), retrieved 2018-10-04, message-ID <email@example.com>: 1977 CHiPs 3 3/4" action figures (5 different: Ponch, Jon, Sarge,Jimmy Squeaks, Stupid Fucking Asshat Erik Mouse, and Wheels Willie) $10-15 each
, 2006 Jen Lancaster, Bitter is the New Black, Penguin, [ … ] , →ISBN page : 224 While I wait, the air is abuzz with tales of other marathons while many set of eyes cut in my direction. Eventually an asshat in a JUST DO IT T-shirt asks me, “How's your training going?” , John Hargrave, 2007 Prank the Monkey: The Zug Book of Pranks , Citadel Press,  , page →ISBN 188: Anyone who would make a claim like this on national TV is a real asshat.