What is this object?

[Utini]

Found yesterday in our utility room, DP and DD have no idea where it has come from.

About the size of a wax crayon, with a square shaped hole at one end and a sticking out bit on the other end with a groove in it.

Does anyone know?

Fluorescent disposable light I.e bought at fireworks displays

It's a glowstick, have you never been to a rave?

No I've never been to a rave! Doesn't look like a glow stick to me though.

It also wouldn't snap like a glow stick, it's completely rigid.