From The Jargon File (version 4.4.7, 29 Dec 2003) :
page in v. [MIT] 1. To become aware of one's surroundings again after having paged out (see page out). Usually confined to the sarcastic comment: ?Eric pages in, { film at 11!? 2. Syn. swap in; see swap.From The Free On-line Dictionary of Computing (30 December 2018) :
page inWhat a paging system does when it copies part of a task's working memory from swap space on disk to RAM. [{Jargon File] (1995-01-23)