Interregnum comes from Latin inter- and regnum. It can name the interval when a throne is vacant between successive reigns, and more broadly a pause in leadership or control.
The prefix inter- is separate from the English burial verb inter, which has another formation.
Sources
- Merriam-Webster: interregnum
Latin interregnum contains inter- and regnum, reign; the modern word covers a vacant throne and broader interruptions.
- Merriam-Webster: inter-
The prefix is borrowed from Latin inter, among or between, separately from the burial verb.
- Online Etymology Dictionary: reign
Also built on *regnum*: reign, from Old French reigne, from Latin regnum "kingship, dominion, rule, realm"