PEBCAK is an informal term that developed organically amongst IT support staff, original source is unknown.  It stands for Problem Exists Between Chair And Keyboard, i.e. in the user.  Sometimes the term ID10T error is used, pronounced Eye-Dee-Ten-Tee but as can be seen spells out idiot when written down.

Both terms represent the traditional disdain that IT support (the 'techies') have for users coupled to the macho atmosphere of IT support that developed during the 1980s and 90s.

In practice most PEBCAK and ID10T error issues are due to poor user training or a mismatch between what the service was designed to do and what the users require it to do.  A common cause of the latter is insufficient Requirements Gathering and Analysis.