An unwanted house guest who invites himself to stay in your home is an example of an interloper.
Origin of interloper
- inter– probably Middle Dutch lōper runner (from lōpen to run)
From American Heritage Dictionary of the English Language, 5th Edition
- 1590s, from inter- + loper (“runner, rover”), as in landloper (“vagrant”) (from Dutch) or lope (“to leap, to jump”) (originally dialectical). Originally spelt enterloper and used in specific sense “unauthorized trader trespassing on privileges of chartered companies”, later general sense of “self-interested intruder” from 1630s.